Methods and reagents for detecting endotoxin

ABSTRACT

A reagent containing a purified horseshoe crab Factor C, Particularly a recombinantly produced Factor C, and a surfactant can be used in a sensitive, rapid, and reproducible assay to detect endotoxin.

[0001] This application claims the benefit of and incorporates by reference copending provisional application Ser. No. 60/310,125 filed Jun. 28, 2001.

FIELD OF THE INVENTION

[0002] The invention relates to reagents and methods for detecting endotoxin.

BACKGROUND OF THE INVENTION

[0003] Gram negative bacterial endotoxin is a widespread contaminant of a variety of materials, such as water, food, pharmaceutical products, and parenteral preparations. The most commonly used tests for endotoxin contamination employ amebocyte lysates derived from horseshoe crab hemolymph. As populations of these animals decreases, however, it becomes increasingly important to develop rapid and reliable methods for detecting endotoxin that do not rely on the availability of horseshoe crab hemolymph.

BRIEF SUMMARY OF THE INVENTION

[0004] The invention provides reagents and methods for detecting endotoxin. One embodiment of the invention is a reagent for detecting endotoxin, comprising a purified horseshoe crab Factor C protein and a surfactant. The surfactant can be an amphoteric surfactant represented by the following formulae:

[0005] wherein R₁ is an alkylene radical having from 1 to 4 carbon atoms; Y and Y′ are each (1) hydrogen, (2) lower alkyl, or (3) hydroxy lower alkyl; R₂ and R₃ are each (1) lower alkyl or (2) hydroxy lower alkyl; n is 0 or 1, when n is 0, R₄ is alkyl containing from about 8 to about 18 carbon atoms; when n is 1, R₄ is an alkylene radical having from 1 to about 6 carbon atoms; R₅ is an allyl containing from about 8 to about 18 carbon atoms; and M is hydrogen, sodium, potassium or ammonium. The surfactant can be an anionic surfactant represented by the following formulae:

(R₆)_(n1-)(Y)Ar(SO₃M)_(n2)  (E)

R₅OSO₃M (F)

[0006] wherein R₅, Y, and M have the same meaning as set forth above; R₆ is an alkyl from 8 to 24 carbon atoms; n1 is an integer from 1 to 3; n2 is 1 or 2; and Ar is phenyl or naphthyl. The surfactant can be a cationic surfactant represented by the following formula:

[0007] wherein R₅, Y, and Y′ have the same meaning as set forth above. The surfactant can be a nonionic surfactant represented by the following formula:

R₅R₇R₉N→O  (H)

[0008] wherein R₅, Y, and Y′ have the same meaning as set forth above and R₇ and R₈ are each methyl or ethyl. The surfactant can be those nonionic surfactants selected from the group consisting of the condensation product of about 10 to 30 moles of ethylene oxide with the monoester of a hexahydric alcohol containing 6 carbon atoms with the ester group containing 10 to 20 carbon atoms.

[0009] Even another embodiment of the invention is a method of detecting endotoxin in a test sample. A test sample is contacted with (1) a reagent comprising (a) a purified horseshoe crab Factor C protein and (b) a surfactant to form a test sample-reagent mixture and (2) a Factor C substrate to form a contacted test sample. Cleavage of the Factor C substrate generates a detectable signal. The contacted test sample is assayed for the presence or absence of the detectable signal. An amount of the detectable signal that is increased relative to a control sample that does not contain endotoxin indicates a presence of endotoxin in the test sample.

[0010] A further embodiment of the invention is a method of detecting endotoxin in a test sample. A test sample is contacted with (1) a reagent comprising (a) a recombinant Carcinoscorpius rotundicauda Factor C protein and (b) a surfactant and (2) N-t-BOC-Asp(Obzl)-Pro-Arg-7-Amido-4-methyl coumarin to form a contacted test sample. The Factor C protein is made by the method of culturing a host cell comprising a vector encoding the Factor C protein in a supernatant under conditions such that the Factor C protein is expressed into the supernatant. The contacted test sample is assayed for the presence or absence of a fluorescent signal. An amount of the detectable signal that is increased relative to a control sample that does not contain endotoxin indicates a presence of endotoxin in the test sample.

[0011] Another embodiment of the invention is a method of detecting endotoxin in a test sample. A test sample is contacted with a reagent comprising a purified horseshoe crab Factor C protein and a surfactant as described above to form a test sample-reagent mixture. The test sample-reagent mixture is contacted with a Factor C substrate, wherein cleavage of the Factor C substrate generates a detectable signal. The contacted test sample-reagent mixture is assayed for the presence or absence of the detectable signal. An amount of the detectable signal that is increased relative to a control sample that does not contain endotoxin indicates a presence of endotoxin in the test sample.

[0012] Even another embodiment of the invention is a method of detecting endotoxin in a test sample. A test sample is contacted with a reagent comprising a recombinant Carcinoscorpius rotundicauda Factor C protein and a surfactant. The Factor C protein is made by the method of culturing a host cell comprising a vector encoding the Factor C protein in a supernatant under conditions such that the Factor C protein is expressed into the supernatant. The test sample-reagent mixture is contacted with N-t-BOC-Asp(Obzl)-Pro-Arg-7-Amido-4-methyl coumarin. The contacted test sample-reagent mixture is assayed for the presence or absence of a fluorescent signal. An amount of the fluorescent signal that is increased relative to a control sample that does not contain endotoxin indicates a presence of endotoxin in the test sample.

[0013] Yet another embodiment of the invention is a kit for detecting endotoxin. The kit comprises a reagent that comprises (a) a purified horseshoe crab Factor C protein and (b) a surfactant as described above, together with instructions for a method of detecting endotoxin in a test sample. The method comprises the steps of (1) contacting a test sample with a reagent comprising (a) a purified horseshoe crab Factor C protein and (b) a surfactant as described above to form a test sample-reagent mixture; (2) contacting the test sample-reagent mixture with a Factor C substrate, wherein cleavage of the Factor C substrate generates a detectable signal; and (3) assaying the contacted test sample-reagent mixture for the presence or absence of the detectable signal, wherein an amount of the detectable signal that is increased relative to a control sample that does not contain endotoxin indicates a presence of endotoxin in the test sample.

BRIEF DESCRIPTION OF THE FIGURES

[0014]FIG. 1. Graph showing effect of Zwittergent 3-14 and Tween 20 on recombinant Factor C activity.

[0015]FIG. 2. Graph showing effect of Zwittergent 3-14 and Tween 80 on recombinant Factor C activity.

[0016]FIG. 3. Graph showing effect of Zwittergent 3-14 and Triton X-114 on recombinant Factor C activity.

[0017]FIG. 4. Plot showing endotoxin detection using a DPR(N-t-BOC-Asp(Obzl)-Pro-Arg-7-Amido-4-methyl)-coumarin substrate.

[0018]FIG. 5. Plot showing endotoxin detection using a VPR(N-t-BOC-Val-Pro-Arg-7-Amido-4-methyl)-coumarin substrate.

[0019]FIG. 6. Graph showing Limulus Factor C activity at different Zwittergent concentrations.

[0020]FIG. 7. Graph showing endotoxin sensitivity in the presence and absence of surfactant.

[0021]FIG. 8. Graph showing results of a one hour, one-step endotoxin assay, using DPR-coumarin as a substrate.

[0022]FIG. 9. Graph showing effect of Zwittergent 3-14 and octylthiolglycoside on recombinant Factor C activity.

[0023]FIG. 10. Graph showing effect of Zwittergent 3-14 and Genapol C-100 on recombinant Factor C activity.

[0024]FIG. 11. Graph showing effect of Zwittergent 3-14 and IX-100 on recombinant Factor C activity.

DETAILED DESCRIPTION OF THE INVENTION

[0025] The invention is a reagent for detecting endotoxin and a method of using the reagent. The reagent comprises a purified horseshoe crab Factor C protein and a surfactant. This reagent can be used in conjunction with a substrate for Factor C that, upon cleavage, generates a detectable signal to detect endotoxin in a test sample. The presence of the surfactant enhances the activation of the purified Factor C by endotoxin by as much as 3-7-fold, permitting more rapid and sensitive measurement of endotoxin levels in a test sample. The reagent preferably contains a recombinant Factor C, thus eliminating the need for a continuous supply of horseshoe crab hemolymph.

[0026] Purified Factor C

[0027] One component of the reagent of this invention comprises a purified horseshoe crab Factor C protein. Purified native Factor C from any of the four known horseshoe crab species, Limulus polyphemus, Carcinoscorpius rotundicauda, Tachypleudus tridentata, or Tachypleudus gigas, can be used in the practice of the invention. The native Factor C can be purified biochemically or purified Factor C can be produced recombinantly.

[0028] “Purified Factor C” as used herein means a composition of a Factor C protein as defined hereinafter that contains less than 30% by weight of non-Factor C native amebocyte lysate components from any of the four known horseshoe crab species. The composition specifically includes a cell culture supernatant which comprises recombinant Factor C protein (see below). Methods for purifying horseshoe crab Factor C from its native source are known and are disclosed, for example, in Nakamura et al., Eur. J. Biochem. 154, 511-21, 1986; Navas et al., Biochem. Intl. 21, 805-13, 1990; Tokunaga et al., J. Biochem. 109, 150-157, 1991; U.S. Pat. No. 5,985,590, and U.S. Pat. No. 5,716,834. Any of these methods or their equivalents can be used to obtain a purified Factor C. See also Example 11. Purity of a Factor C preparation can be assessed by any means known in the art, such as SDS gel electrophoresis.

[0029] Preferably, the purified Factor C is recombinantly produced. Amino acid sequences for native Factor C from Tachypleus tridentata and Carcinoscorpius rotundicauda are known, as are the naturally occurring coding sequences for these proteins. SEQ ID NOS:1 and 3 provide coding sequences for the Tachypleus tridentata Factor C amino acid sequences shown in SEQ ID NOS:2 and 4, respectively. SEQ ID NOS:5 and 7 provide coding sequences for the Carcinoscorpius rotundicauda Factor C amino acid sequences shown in SEQ ID NOS:6 and 8, respectively. Because of the degeneracy of the genetic code, many other sequences can be envisioned that will encode each of these native Factor C proteins, and the invention specifically contemplates use of any of these coding sequences to produce a purified Factor C.

[0030] The invention also encompasses use of purified naturally and non-naturally occurring, i.e., recombinantly produced, Factor C variants, provided that the variants retain a Factor C enzyme activity. Factor C enzyme activity can be assessed using any assay for Factor C enzyme activity known in the art. See, e.g., Tokunaga et al., J. Biochem. 109, 150-57 (1991) and Nakamura et al., Eur. J. Biochem. 176, 89-94, 1988. The endotoxin assays described in Examples 1 and 13, below, also can be used. Naturally occurring Factor C variants include, for example, products of Factor C mRNA splice variants or mutated Factor C genes.

[0031] Non-naturally occurring Factor C variants can be constructed using base substitutions, additions, or deletions to produce proteins having Factor C activity. Non-naturally occurring Factor C variants can differ from naturally occurring Factor C by as much as 50, 75, 80, 85, 90, 95, 97, 98, or 99%, as determined using the Blast2 alignment program (Blosum62, Expect 10, standard genetic codes). Fragments of native and recombinantly produced Factor C that retain Factor C activity also can be used in the practice of the invention. Thus, “Factor C” as used herein includes naturally and non-naturally occurring proteins and protein fragments that have the properties described above.

[0032] Methods of producing proteins recombinantly are well known in the art and generally involve culturing a host cell comprising an expression vector encoding the Factor C protein in a supernatant under conditions such that the protein is expressed. The expressed protein can be recovered or, preferably, the supernatant comprising the expressed protein is used directly as the source of recombinant Factor C. Thus, “purified Factor C” specifically includes a supernatant which comprises recombinant Factor C. Host cells useful for the production of recombinant Factor C include, without limitation, yeast cells and insect cells. Recombinant production of Carcinoscorpius rotuidicauda Factor C in Pichia pastoris and Saccharomyces cerevisiae host cells is specifically disclosed in U.S. Pat. No. 5,985,590.

[0033] A particularly preferred method of obtaining recombinant Factor C is to produce the protein in a baculovirus system, as described in Examples 2-5. Briefly, a Factor C coding sequence is cloned into pFASTBAC1. The resultant recombinant plasmid is transformed into DH10BAC competent cells that contain a bacmid with a mini-attTn7 target site and a helper plasmid. In the presence of transposition proteins provided by the helper plasmid, the mini-Tn7 transposable element on the pFASTBAC plasmid can transpose to the mini-attTn7 target site on the bacmid. Colonies containing recombinant bacmids are identified by disruption of the lacZa gene. High molecular weight DNA is prepared from selected DH10BAC clones containing the recombinant bacmid. This DNA is then used to transfect S9 insect cells, which will then secrete recombinant Factor C. A particularly surprising discovery of the present invention is that culture medium containing the secreted Factor C, which has been separated from the cultured cells, can be used together with a surfactant (described below) as a reagent in endotoxin assays without further purification.

[0034] Surfactant

[0035] Reagents of the invention also comprise a surfactant. Surfactants useful in the practice of the invention include those described in U.S. Pat. No. 4,322,217, although other surfactants also can be used. Useful surfactants include amphoteric surfactants that contain both an anionic and cationic group in their structure. Illustrative are the sulfobetaines represented by Formula A:

[0036] R₁ is an alkylene radical having from 1 to about 4 carbon atoms,

[0037] Y is any non-deleterious, chemically suitable substituent including (1) hydrogen, (2) substituted or unsubstituted lower alkyl, e.g., containing 1 to 4 carbon atoms such as methyl, ethyl, propyl, or hydroxy etc.;

[0038] R₂ and R₃ are each selected from substituted or unsubstituted lower alkyl containing 1 to 4 carbon atoms, e.g., such as methyl, ethyl, propyl, hydroxy ethyl, hydroxy methyl, hydroxy propyl, etc.

[0039] n=0, or 1,

[0040] when n=0, R₄ is substituted or unsubstituted alkyl, e.g., containing about 8 to about 18 carbon atoms, and

[0041] when n=1, R₄ is an alkylene radical having from about 1 to about 6 carbon atoms, R₅ is a substituted or unsubstituted alkyl, e.g., containing about 8 to about 18 carbon atoms.

[0042] The term “alkylene” encompasses both polymethylene radicals and other divalent saturated aliphatic radicals. Thus, there may be branching in the linkage provided by the alkylene radical. The term “lower” means a radical containing 1 to 4 carbon atoms.

[0043] Sulfobetaines that can be used in the reagent of the present invention are known in the art and have been described as zwitterionic surfactants. The preparation of such compounds is described for example, in Fernley, J. Am. Oil Chem. Soc. 55, 98-103 (1978) and U.S. Pat. No. 3,280,179. In preferred sulfobetaine surfactants, R₂ and R₃ in the above structure are methyl. It is also preferred that R₁ be propylene.

[0044] One type of useful sulfobetaine surfactant has the above structure wherein n equals 0 and R₄ is an alkyl radical having from about 8 to 18 carbon atoms, preferably a straight chain alkyl radical. For these sulfobetaine surfactants, a convenient source of the R₄ component is tallow fatty alcohol, which consists of a mixture of various chain lengths, with a typical composition being approximately 66 percent C₁₈, 30 percent C₁₆, and 4 percent C₁₄ and others. Another convenient source is the middle cut of distilled coconut fatty alcohol, which also consists of a mixture of various chain lengths, with a typical composition being approximately 66 percent C₁₂, 23 percent C₁₄, 9 percent C₁₆ and 2 percent C₁₀.

[0045] Specific sulfobetaine surfactants of the above structure wherein n equals 0 are set forth in U.S. Pat. No. 3,539,521. A particularly preferred surfactant of this type is N-tetradecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, which is commercially available from Calbiochem-Behring Corporation under the trademark ZWITTERGENT 3-14.

[0046] Another type of useful sulfobetaine surfactant has the above structure wherein n equals 1 and R₄ is an alkylene radical having from about 1 to about 6 carbon atoms. In these sulfobetaines wherein n equals 1, R₅ is an alkyl radical having from about 8 to about 18 carbon atoms. It is preferred that R₅ be straight chain. As previously discussed, convenient sources of alkyl radicals having from about 10 to about 18 carbon atoms are tallow fatty alcohol and coconut fatty alcohol. Specific sulfobetaine surfactants of the above structure wherein n equals 1 are set forth in U.S. Pat. No. 3,280,179.

[0047] Particularly preferred sulfobetaine surfactants are 3-(N,N-dimethyl-N-acylamidopropylammonio)-2-hydroxy-propane-1-sulfonates, wherein the acyl group is derived from tallow fatty alcohol or coconut fatty alcohol, with coconut fatty alcohol preferred. It will be recognized by those skilled in the art that, in the normal preparation of these derivatives of tallow or coconut fatty alcohols, a mixture of sulfobetaines with varying carbon chain lengths for the acyl groups will result. As previously discussed, these fatty alcohols contain, for the most part, carbon chain lengths that will provide acyl groups with the desired number of carbon atoms, i.e., from about 8 to about 18 carbon atoms. Thus, these mixtures obtained from tallow or coconut fatty alcohols are useful in providing the sulfobetaine surfactant for reagents of the present invention.

[0048] A material of this type particularly preferred for use in reagents of the present invention is N-cocoamido-propyl-N,N-dimethyl-N-2-hydroxypropyl sulfobetaine. An example of this is LONZAINE CS, which is commercially available from Lonza, Inc., Fair Lawn, N.J.

[0049] Other amphoteric surfactants include the N-long chain alkyl aminocarboxylic acids illustrated by Formula B:

[0050] N-long chain alkyl iminodicarboxylic acids illustrated by Formula C:

[0051] and N-long chain alkyl or amido betaines illustrated by Formula D:

[0052] where R₁, R₂, R₃, R₄, Y, and n have the same meaning as they have in Formula A, M is hydrogen or a salt-forming metal, and Y′ has the same meaning as Y in Formula A. Y and Y′ may be the same or different. Examples of specific amphoteric detergents are N-alkylbeta-aminopropionic acid, N-alkyl-beta-iminodipropionic acid, and N-alkyl-N,N-dimethyl glycine; the alkyl group may be, for example, that derived from coco fatty alcohol, lauryl alcohol, myristyl alcohol (or a lauryl-myristyl mixture), hydrogenated tallow alcohol, cetyl, stearyl, or blends of such alcohols. The substituted aminopropionic and iminodipropionic acids are often supplied in the sodium or other salt forms, which also can be used in reagents of the invention.

[0053] Specific examples include cocobetaine sold by Witco Chemical Corporation under the name EMCOL CC 37-18, cocoamidopropyl betaine sold by Lonza Inc. under the name LONZAINE CO, and disodium N-tallow-beta-iminodipropionate sold by Henkel Corporation under the name of DERIPHAT 160.

[0054] Examples of other amphoteric detergents are the fatty imidazolines such as those made by reacting a long chain fatty acid (e.g., of 10 to 20 carbon atoms) with diethylene triamine and monohalocarboxylic acids having 2 to 6 carbon atoms, e.g. 1-coco-5-hydroxyethyl-5-carboxymethylimidazoline. Specific examples include cocoimidazoline, which is commercially available under the name AMPHOTERGE K-2 from Lonza, Inc., and capric dicarboxy imidazoline, which is commercially available under the name AMPHOTERGE KJ-2 from Lonza, Inc.

[0055] Other examples of useful surfactants include anionic synthetic surfactants, generally described as those compounds that contain hydrophilic and lipophilic groups in their molecular structure and ionize in an aqueous medium to give anions containing both the lipophilic group and hydrophilic group. The alkyl aryl sulfonates, the alkane sulfates, and sulfated oxyethylated alkyl phenols are illustrative of the anionic type of surface active compounds.

[0056] The alkyl aryl sulfonates are a class of synthetic anionic surface active agents represented by Formula E:

(R₆)_(n1-)(Y)Ar(SO₃M)_(n2)  (E)

[0057] In Formula E, R₆ is a straight or branched chain hydrocarbon radical having from about 1 to about 24 carbon atoms, at least one R₆ having at least 8 carbon atoms; n1 is from 1 to 3; n2 is from 1 to 2; Ar is a phenyl or a naphthyl radical, and Y and M have the same meaning as in Formula B. R₆ can be, for example, methyl, ethyl, hexyl, octyl, tetraoctyl, iso-octyl, nonyl, decyl, dodecyl, octadecyl, and the like.

[0058] Compounds illustrative of the alkyl aryl sulfonates include sodium dodecylbenzene sulfonate, sodium decylbenzene sulfonate, ammonium methyl dodecylbenzene sulfonate, ammonium dodecylbenzene sulfonate, sodium octadecylbenzene sulfonate, sodium nonylbenzene sulfonate, sodium dodecylnaphthalene sulfonate, sodium hetadecylbenzene sulfonate, potassium eicososyl naphthalene sulfonate, ethylamine undecylnaphthalene sulfonate and sodium docosylnaphthalene sulfonate.

[0059] The alkyl sulfates are a class of synthetic anionic surface active agents represented by Formula F:

R₅OSO₃M  (F)

[0060] where R₅ and M have the same meaning as in Formula B. Compounds illustrative of alkyl sulfate class of anionic surfactants include sodium octadecyl sulfate, sodium hexadecyl sulfate, sodium dodecyl sulfate, sodium nonyl sulfate, ammonium decyl sulfate, potassium tetradecyl sulfate, diethanolamino octyl sulfate, triethanolamine octadecyl sulfate, and ammonium nonyl sulfate.

[0061] The sulfated oxyethylated alkylphenols are a class of synthetic anionic surface active agents represented by Formula G:

[0062] where A is either oxygen, sulfur, a carbonamide group, a thiocarbonamide group, a carboxylic group, or a thiocarboxylic ester group, z is an integer from 3 to 8, and R₅ and M have the same meaning as in Formula B. Compounds illustrative of the sulfated oxyethylated alkyl phenol class of anionic surfactants include ammonium nonylphenoxyl tetraethylenoxy sulfate, sodium dodecylphenoxy triethyleneoxy sulfate, ethanolamine decylphenoxy tetraethyleneoxy sulfate, and potassium octylphenoxy triethyleneoxy sulfate.

[0063] Other examples of useful surfactants include nonionic surface active compounds, which can be broadly described as compounds that do not ionize but acquire hydrophilic characteristics from an oxygenated side chain, such as polyoxyethylene; the lipophilic part of the molecule may come from fatty acids, phenol, alcohols, amides, or amines. The compounds are usually made by reacting an alkylene oxide, such as ethylene oxide, butylene oxide, propylene oxide and the like, with fatty acids, straight or branched chain alcohols containing one or more hydroxyl groups, phenols, thiophenols, amides, or amines to form polyoxyalkylene glycoethers and esters, polyoxyalkylene alkylphenols, polyoxyalkylene thiophenols, polyoxyalkylene amides and the like. It is generally preferred to react from about 3 to about 30, more preferably 10 to 30, moles of alkylene oxide per mole of the fatty acids, alcohols, phenols, thiophenols, amides, or amines.

[0064] Illustrative of these nonionic surfactants are the products obtained from the reaction of alkylene oxide with an aliphatic alcohol having from 8 to 18 carbon atoms, such as octyl, nonyl, decyl, octadecyl, dodecyl, tetradecyl and the like, with monoesters of hexahydric alcohols, the ester group containing 10 to 20 carbon atoms such as sorbitan monolaureate, sorbitan monooleate and sorbitan monopalmitate, with an alkyl phenol in which the alkyl group contains between 4 and 20 carbon atoms, such as butyl, dibutyl, amyl, octyl, dodecyl, tetradecyl, and the like, or with an alkyl amine in which the alkyl group contains between 1 to 8 carbon atoms.

[0065] Compounds illustrative of synthetic nonionic surfactants include the products obtained from condensing ethylene oxide or propylene oxide with the following: propylene glycol, ethylene diamine, diethylene glycol, dodecyl phenol, nonyl phenol, tetradecyl alcohol, N-octadecyl diethanolamide, N-dodecyl monoethanolamide, polyoxyethylene (20) sorbitan monooleate sold under the name TWEEN 80 and polyoxyethylene (20) sorbitan monolaurate sold under the name TWEEN 20.

[0066] Other nonionic surfactants include long chain tertiary amine oxides corresponding to Formula H:

R₅R₇R₈N→O  (H)

[0067] wherein R₅ has the same meaning as in Formula A, and R₇ and R₈ are each methyl or ethyl radicals. The arrow in the formula is a conventional representation of a semi-polar bond. Examples of amine oxides suitable for use in this invention include dimethyldodecylamine oxide, dimethyloctylamine oxide, dimethyldecylamine oxide, dimethyltridecylamine oxide, and dimethylhexadecylamine oxide.

[0068] Cationic surface active agents can also be used as surfactants. Such agents are those surface-active compounds which contain an organic hydrophobic group and a cationic solubilizing group. Typical cationic solubilizing groups are amine and quaternary groups. Such cationic surface-active agents are represented by Formula I:

[0069] wherein R₅, Y, and Y′ have the same meaning as in Formula C.

[0070] Other examples of suitable synthetic cationic surfactants include the diamines such as those of Formula J:

R₉NHC₂H₄NH₂  (J)

[0071] wherein R is an alkyl group of about 12 to 22 carbon atoms, such as N-2-aminoethyl stearyl amine and N-2-aminoethyl myristyl amine; amide-linked amines such as those of Formula K:

R₅CONHC₂H₄NH₃  (K)

[0072] such as N-2-amino ethylstearyl amide and N-amino ethyl myristyl amide; quaternary ammonium compounds wherein typically one of the groups linked to the nitrogen atom are alkyl groups which contain 1 to 3 carbon atoms, including such 1 to 3 carbon alkyl groups bearing inert substituents, such as phenyl groups and there is present an anion such as halogen, acetate, methylsulfate, etc. Typical quaternary ammonium compounds are ethyl-dimethylstearyl ammonium chloride, benzyl-dimethyl-stearyl ammonium chloride, benzyldimethyl-stearyl ammonium chloride, trimethyl stearyl ammonium chloride, trimethylcetyl ammonium bromide, dimethylethyl dilaurylammonium chloride, dimethyl-propyl-myristyl ammonium chloride, and the corresponding methosulfates and acetates.

[0073] Another suitable cationic surfactant is represented by Formula L:

[0074] wherein R₅ has the same meaning as in Formula A and each a is an integer from 1 to 15. An example is the polyethylene glycol amine of hydrogenated tallow wherein R₅ represents the tallow radical and a+a has an average value of 5.

[0075] Other useful surfactants for use in the Factor C-surfactant reagent include Triton X-100, Triton X-114, octyl-beta-D-thioglucoside (OTG, Amresco #J575), Genapol C-100 (an alkyl polyoxyethylene C12E10; Calbiochem #345794), Tween 20, and Tween 80.

[0076] Factor C-Surfactant Reagent

[0077] To form a reagent of the invention, purified Factor C and a surfactant are combined in an aqueous solution. A suitable buffer solution for this purpose contains 30 mM Tris, pH 8.0, 30 mM NaCl, and 0.3% lactose. The concentration of purified Factor C in a reagent of the invention preferably ranges from 0.03-3 μg/ml. The concentration of surfactant in the reagent of the invention preferably ranges from 0.001-0.003%. Optimum concentrations of purified Factor C and of the surfactant will vary, depending, for example, on the purity of the Factor C and the particular surfactant. Optimum concentrations of purified Factor C and of surfactant can be determined using routine testing. In the assay exemplified in Examples 1 and 13, the optimal concentration of the surfactant ZWITTERGENT 3-14 is 0.0025%.

[0078] Endotoxin Assay

[0079] The reagent described above can be used in an assay to detect endotoxin in a test sample. The test sample can be any sample in which it would be useful to detect endotoxin, including water, aqueous solutions such as buffers, pharmaceutical preparations (e.g., vaccines, intravenous fluids, drug preparations), biomedical imaging reagents (e.g., dyes, radioactive solutions), enzyme preparations (e.g., collagenase), tissue culture media, beverages, blood, urine, cerebrospinal fluid, lymph, serum, and solutions formed by incubating water or an aqueous solution with a solid sample, such as a foodstuff or a surgical glove.

[0080] Either a two-step or a one-step assay can be performed. To perform the two-step assay (Example 1), a test sample is incubated with a reagent containing purified Factor C and a surfactant, then a Factor C substrate that will generate a detectable signal upon cleavage is added. To perform the one-step assay (Example 13), endotoxin, the reagent containing purified Factor C and a surfactant, and a substrate are added together.

[0081] Substrates that will generate a fluorescent signal upon cleavage are particularly preferred, such as N-t-BOC-Asp(Obzl)-Pro-Arg-7-Amido-4-methyl coumarin (“DPR,” Bachem 1-1560.0050) and N-t-BOC-Val-Pro-Arg-7-Amido-4-methyl coumarin (“VPR,” Bachem 1-1120.0050). Concentrations of DPR generally range from about 10-100 mM, 25-100 mM, 5-100 mM, 75-100 mM, 25-75 mM, 50-75 mM, 25-50 mM, or 50-75 mM. Concentration of VPR generally range from about 50-200 mM, 50-150 mM, 50-100 mM, 50-75 mM, 75-150 mM, or 75-100 mM.

[0082] The optimum concentration for a particular substrate varies. For example, the optimum concentration for DPR is 50 mM, whereas the optimum concentration for VPR is 100 mM. Moreover, the particular substrate can be chosen depending on the endotoxin levels expected to be present in the test sample. The VPR substrate has a better linear range at higher endotoxin concentrations, and the DPR substrate has a better linear range at lower endotoxin concentrations. Thus, DPR can be used in assays in which higher sensitivity is desired, whereas VPR is the preferred substrate when higher endotoxin levels are expected to be present and a lower sensitivity is required.

[0083] Fluorescence can be measured using any means known in the art. If a fluorimeter is used with the DPR or VPR substrates described above, the excitation is set at 360, 380, 390, or 395 nm (slit width of 540 nm) and the emission is measured at 440 or 460 nm (slit width of 2.5-40 nm). Measurement can be either qualitative or quantitative, by reference to a standard endotoxin concentration curve.

[0084] The assay can be carried out in a clear vessel, such as a glass or polystyrene tissue culture plate, or can be carried out in a black vessel (e.g., a black 96-well microplate). If desired, the assay can be adapted for high-throughput screening of multiple samples using, for example, 96-well microtiter plates.

[0085] Kits

[0086] The invention also provides a kit for use in detecting endotoxin. The kit comprises a purified horseshoe crab Factor C protein and a surfactant, as described above. Instructions for using the reagent to detect endotoxin can be included. Kits also can include a Factor C substrate for use in the assay.

[0087] All patents, patent applications, and references cited in this disclosure are expressly incorporated herein by reference. The above disclosure generally describes the present invention. A more complete understanding can be obtained by reference to the following specific examples, which are provided for purposes of illustration only and are not intended to limit the scope of the invention.

EXAMPLE 1

[0088] Two-Step Endotoxin Assay

[0089] Endotoxin was pre-incubated with culture medium containing recombinant Carcinoscorpius rotundicauda Factor C obtained from recombinant Factor C-producing Sf9 cells for 1 hour in assay buffer (30 mM Tris, pH 8.0, 30 mM NaCl, 0.3% lactose, and 0.0025% Zwittergent 3-14). The substrate N-t-Boc-Asp(Obzl)-Pro-Arg-7-Amido-4-methyl coumarin (DPR-coumarin) was added to the mixture to a final concentration of 50 mM. The fluorescence generated from the cleavage of the substrate by activated Factor C was measured after 15-20 minutes. The results are shown in FIG. 4. Results of a similar assay carried out using the substrate N-t-Boc-Val-Pro-Arg-7-Amido-4-methyl coumarin at a final concentration of 100 mM are shown in FIG. 5.

EXAMPLE 2

[0090] Transfection of Bacmid DNA-Factor C into Sf9 Cells and Harvesting of Recombinant Viral Supernatant

[0091] Sf9 cells are seeded at a density of 5×10⁶ per 35 mm well in a 6-well tissue culture plate in insect cell culture medium (ICCM) containing 50 U/ml penicillin and 50 mg/ml streptomycin. Insect-Xpress (BioWhittaker Cat. #04-10270) or Sf-900 SFM are suitable media; however, any comparable medium in which SF9 cells grow can be used. The plates are incubated at 27° C. for 1 hour to allow the cells to settle. Meanwhile, the following are prepared (each per well): (1) 7 mg of bacmid-Factor C DNA in 100 ml ICCM (without antibiotics) and (2) 6 ml CELLFECTIN (Gibco-BRL) plus 100 ml ICCM (without antibiotics). Solutions (1) and (2) are mixed gently and incubated at room temperature for one hour. To this mixture, 0.8 ml of ICCM (without antibiotics) is added.

[0092] The adhered Sf9 cells are washed gently with 2 ml ICCM (without antibiotics). One ml of CELLFECTIN-DNA complex is added to each well and incubated at 27° C. for 5 hours. The transfection mixtures are removed completely, and 2 ml of ICCM containing antibiotics is added. After incubation at 27° C. for 96 hours, the cell culture supernatant is harvested. The supernatant is clarified by centrifugation at 5000 rpm for 10 minutes in a SIGMA 3K10 swing-out rotor, Nr. 11133. The supernatant, containing the recombinant baculovirus, is stored at 4° C.

EXAMPLE 3

[0093] Amplifcation of Recombinant Viral Stock

[0094] Virus amplification can be done with Sf9 cells either in a monolayer or in suspension. For monolayer culture, the medium is decanted from a culture of 80% confluent one day-old Sf9 cells in a 75 cm² tissue culture flask. The cell monolayer is infected with 1 ml of virus (Example 2) using an MOI of 0.1-1. The virus stock is sterile-filtered using a Millipore GV millex filter (yellow; low-protein binding). Calculation of the viral inoculum is as follows: ${{volume}\quad {of}\quad {inoculum}} = \frac{{MOI} \times {total}\quad {cell}\quad {number}}{{virus}\quad {titer}\quad {in}\quad {pfu}\text{/}{ml}}$

[0095] Thus, for 1×10⁷ cells, at a virus titer of 2×10⁷ pfu/ml, the volume of the inoculum is 0.5 ml. The volume of the inoculum is adjusted to 1 ml with ICCM before it is introduced to the cells.

[0096] The flask is rocked several times to ensure that the cell monolayer is completely covered by the 1 ml viral inoculum. The flask is then incubated at 27° C. for one hour without rocking. After the incubation, the flask is placed upright, and 14 ml of fresh ICCM is added. The flask is then incubated for 3 days at 27° C.

[0097] The culture supernatant is harvested into sterile pyrogen-free tubes and centrifuged at 2000 rpm for 10 minutes at 4° C. using a Sigma 3K10 swing out rotor. For immediate use, the viral stock is stored at 4° C. For long-term storage, the viral stock is placed at −80° C.

[0098] For suspension culture, use log-phase grown Sf9 cells with viability >95% for vial amplification. Cell density and viability are determined. Sf9 cells are diluted with fresh InsectXPRESS to 1×10⁶ cells per ml. Virus to be amplified is added to the Sf9 culture, at an MOI of 0.02 (virus/cell), as follows: ${{{Vol}.\quad {of}}\quad {inoculum}\quad {virus}\quad {stock}\quad ({ml})} = \frac{\left( {{Total}\quad {cells}\text{/}{ml}} \right) \times \left( {{Total}\quad {{Vol}.\quad {of}}\quad {culture}} \right) \times ({MOI})}{\left( {{Virus}\quad {titer}\quad {in}\quad {pfu}\text{/}{ml}} \right)}$

[0099] Spinner flasks are incubated for three days at 27° C.+/−2° C., with constant stirring at 90-120 rpm. The cell culture is transferred to sterile centrifuge bottles and centrifuged at 2000 rpm for 10 minutes at 4° C. The supernatant is collected into a sterile container and discard the cell pellet. The supernatant is filtered through a 0.45 μm filter into a sterile container. The supernatant is further filtered through a sterile, 0.2 μm filter into a sterile container. The finished virus stock is stored protected from light at 2-8° C. A titer determination is performed as explained in Example 4.

EXAMPLE 4

[0100] Titration of Baculovirus

[0101] Virus titer (Plaque Forming Units (PFU) per ml) can be determined with plaque assay, end-point dilution, or other viral titer kits (e.g., BacPAK Baculovirus Rapid Titer Kit by Clontech #K1599-1). Plaque assay is performed in immobilized monolayer culture. Plaque assays to be are performed are determined as follows:

Plaque assay number=Number of viral dilution×4 (quadruplicates)+2 positive and 2 negative controls.

[0102] For example, 10⁵, 10⁶, 10⁷, 10⁸ for viral dilution, each dilution in quadruplicate wells, would be a 16-well plaque assay. Include two positive controls and two negative controls in the plaque assay, for a total of 20 wells.

[0103] Prepare a cell suspension of 5×10⁵ cells per ml density in 10% FBS serum media. Seed 6-well plates at 2 ml per well with above cell suspension. Cells are allowed to attach two hours before experiments. Cells are ˜80% confluent.

[0104] Prepare 10-fold serial viral dilutions using 4.5 ml media and 0.5 ml of viral stock in sterile 15-ml tubes. Aspirate the medium from each well. Add viral dilution 1 ml per well and incubate at 27° C. for 2 hours.

[0105] Warm 1.3×SF-900II (Gibco-BRL #10967-032) to 27° C. Melt 4% agarose (Gibco 18300-012) and keep in 50° C. water-bath. Add 1.3× media and 4% agarose in 3:1 ratio to make 1% agarose in culture media. Keep this agar in a 40° C. water-bath (for example, in a beaker that can be brought to a hood).

[0106] Working quickly so that the agarose mixture does not solidify, aspirate the viral solution from the cell monolayers. Add 2 ml 1% agarose to each well. Let the plates sit in the hood with the covers slightly open for 10 minutes. Invert the plates and put them in a sealed box with damp paper towels to provide humidity. Incubate at 27° C. for 5-7 days, or until plaques are well formed.

[0107] At day 7 of post-infection, add 0.5 ml 0.033% neutral red (in water), incubate 3 minutes, and discard. Alternatively, add 0.5 ml 0.1% trypan blue (in water), rock to cover, sit 3 minutes, and discard. Incubate the plates for 2 hours. With the help of a light box and a magnifier, count the plaques on each plate. Virus titer is calculated using the following formula:

Virus titer (pfu/ml)=# of plaques×viral dilution.

EXAMPLE 5

[0108] Infection of Sf9 Cells for Recombinant Factor C Production in Serum-Free Cultures

[0109] High viability Sf9 cells are used (e.g., viability of 95-100% in serum-free conditions). Culture log-phase Sf9 cells to a cell density of between 1.5×10⁶ and 2.5×10⁶ cells per ml in suspension culture. Recombinant factor C production also can be carried out by infecting Sf9 cells grown in monolayer culture. Determine cell density and viability. Dilute Sf9 cells with fresh InsectXPRESS to 1.5×10⁶ cells per ml. Add recombinant baculovirus high titer stock to the Sf9 culture, at an MOI of 1 (virus/cell), as follows: ${{{Vol}.\quad {of}}\quad {inoculum}\quad {HTS}\quad ({ml})} = \frac{\left( {{Total}\quad {cells}\text{/}{ml}} \right) \times \left( {{Total}\quad {{Vol}.\quad {of}}\quad {culture}} \right) \times ({MOI})}{\left( {{Virus}\quad {Titer}\quad {in}\quad {pfu}\text{/}{ml}} \right)}$

[0110] Harvest culture supernatant seventy-two hours post-infection. Transfer the cell culture to sterile centrifuge bottles and centrifuge at 2000 rpm for 10 minutes at 4° C. Collect the supernatant into a sterile container and discard the cell pellet. Filter the supernatant through a 0.45 μm filter into a sterile container. Further filter supernatant through a sterile, 0.2 μm filter into a sterile container. This culture supernatant, which contains recombinant Factor C, can be stored at 4° C. for up to one year and can be used directly to form a reagent for endotoxin detection in accordance with the present invention.

EXAMPLE 6

[0111] Culture and Subculture of Sf9 Cells Adapted in Serum-Free Medium

[0112] Sf9 cells grow at 27° C. without CO₂. Maximal aeration is preferred. If spinner culture bottles are used, loosen the side screw-caps to increase aeration. Sf9 cells adapted to grow in serum-free medium should be subcultured at 4-5 days intervals on a routine basis.

[0113] Subculture at 5.0×10⁵ cells/mil in a 250 ml spinner or shake flask containing 100 ml of medium with loosened caps to provide maximal aeration. Stir the culture at 90-100 rpm. Cell viability should be above 90%.

[0114] Remove 45 day old cultures from the 27° C. incubator and swab with 70% alcohol. Take an aliquot of cell suspension to determine cell viability and total cell count using trypan blue dye. Determine the cell dilution necessary to obtain 5×10⁵ cells/ml. Swirl the stock culture flask several times and remove the appropriate volume of cell suspension based on the calculation. Inoculate a new 250 ml spinner flask containing enough pre-warmed fresh medium necessary to make up the final culture volume to 100 ml. Place the cultures back into the incubator. Set the stirring speed to 90-100 rpm.

EXAMPLE 7

[0115] Cryopreservation of Serum-Free Cultures of Sf9 Cells

[0116] Grow Sf9 cells either in a monolayer or in suspension. Harvest the cells at mid-log phase of growth (about 2 days) at a viability of >90%. Keep conditioned medium on ice and sterile-filter.

[0117] Determine the cell viability using the trypan blue dye exclusion method. Calculate the required volume of cryopreservation medium (7.5% DMSO in 50% fresh serum-free ICCM medium and 50% conditioned medium; sterile-filtered) to yield a final density of 1-2×10⁷ cells/ml. Hold the cryopreservation mixture on ice. Meanwhile, centrifuge cells from the suspension for 3 minutes at 800 rpm/500×g. Discard the sample if a lot of cells are unpelleted and in the supernatant.

[0118] Resuspend the cell pellet in the determined volume of chilled cryopreservation mix to obtain 1-2×10⁷ cells/ml. Quickly dispense 1-1.5 ml aliquots of cell suspension into cryovials. Freeze the cells at −70 to −90° C. for 4 hours on the upper gaseous phase of liquid nitrogen. Plunge the vials into liquid nitrogen.

EXAMPLE 8

[0119] Recovery of Cryopreserved Serum-Free Sf9 Cells

[0120] Thaw vial by rapid agitation in 37° C. water bath just until melted. Remove the vial from the water bath and swab with sterile 70% isopropanol. Open vial, remove contents of the vial into a sterile centrifriuge tube of appropriate size; and dilute the cell suspension with 5 volumes of InsectXPRESS medium (or equivalent) that has been equilibrated to 27° C.+/−2° C. in an incubator. Centrifuge the diluted suspension at 125×0 for 10 minutes. Discard the fluid and resuspend the cells in a volume of culture medium equal to fluid discarded. Determine cell count and viability. Adjust viable cell density to between 2×10⁵ cells per ml and 3×10⁵ cells per ml using serum free medium. Transfer flask in a 27° C.+/−2° C. incubator on a rotary platform shaker set for continuous shaking and 100-125 revolutions per minute. When the viable cell count of the culture doubles at least every 26 hours, the culture may be expanded as described in Example 6.

EXAMPLE 9

[0121] Adaptation of Sf9 Cells to Suspension Culture

[0122] Six to ten confluent 75 cm² monolayer T-flasks of Sf9 cells are required to initiate a 100 ml suspension culture. Dislodge cells from the bottom of the flasks by holding a flask in one hand and tapping it against the palm of the other hand. Pool the cell suspension and perform a viability count.

[0123] Dilute the cell suspension to approximately 5×10⁵ viable cells/ml at room temperature using complete serum-supplemented or serum-free growth medium contained in a 250 ml spinner flask. The top of the stirrer blade may be slightly above the cell suspension. This provides additional aeration. The side arm caps should be loosened by one-quarter turn.

[0124] Incubate the cells at 27° C. at a constant stirring rate of 100 rpm. Subculture when the viable cell count reaches 1-2×10⁶ cells/ml (3-7 days post-seeding), increase stirring speed by 5 rpm per passage until culture viability is >80%. Repeat until a stirring speed of 100 rpm is achieved for the spinner flask or 130-140 rpm is achieved for the shaker flask cultures. At this point, reduce seeding density to 3×10⁵ cells/ml during subculture.

[0125] If large clumps of cells persist (e.g., >10 cells per clump), let the spinner/shaker flask stand 2-3 minutes without stirring prior to subculturing. This allows larger clumps to settle to the bottom. Pool the upper one-third of the suspension cells for counting and seeding into new cultures. This procedure selects for a cell population that grows as single cells. It may be necessary to repeat this step 2-3 times until clumping is reduced.

EXAMPLE 10

[0126] Effect of Different Detergents and Different Concentrations of Detergents on the Recombinant Factor C Assay

[0127] Materials and Methods

[0128] The following reagents were purchased from the manufacturers indicated: Zwittergent 3-14 (Calbiochem, Cat# 693017), Tween 20 (ICN, Cat# 194841), Tween 80 (ICN, Cat# 194842), Triton X-114 (ICN, Cat# 193971), ), n-Octyl-beta-D-thioglycopyranoside (OTG, Amresco, Cat# J575), and Triton X-100 (ICN, Cat# 194854). The recombinant Factor C (rFC) assay was carried out using 20 μl of each detergent (˜10× of final concentration), 150 μl of 1 EU/ml EC-6, 10 μl of rFC supernatant 031901I, 20 μl of 300 mM Tris, pH 8.0, and 20 μl of 0.55 mM DPR-coumarin substrate. The results of the assay were read at 38° C. using a Cytofluor reader set at 390/440 nm, 5 minutes per cycle, for 1 hour. The data were graphed after 30 minutes.

[0129] Results

[0130] As shown in FIGS. 1-3 and 9-11, low concentrations of Zwittergent 3-14, Tween 20, Tween 80, Triton X-114, OTG, Genapol C-100 and Triton X-100 enhanced the rFC assay 2-7 fold. The enhancing concentration range for Zwittergent 3-14, Triton X-114, OTG and Triton X-100 is narrow, while the enhancing concentration range for Tween 20, Tween 80 and Genapol C-100 is wide.

[0131] Table 1 summarizes the results obtained by testing nine detergents. These detergents can be divided into three groups: detergents that have a narrow concentration range for enhancing recombinant Factor C activity, detergents that have wide concentration range for enhancing recombinant Factor C activity, and detergents that inhibit recombinant Factor C activity. TABLE 1 Detergent concentration range for rFC CMC Cate- Detergents rFC enhancing inhibition (mM) MW gory Group 1 Zwittergent 0.001-<0.004% >=0.004% 0.1-0.4 363.6 ZW Triton X-100 0.001-<0.008% >=0.008% 0.2-0.9 631 Non- ionic Triton X-114 0.001-<0.016% >=0.016% 0.35 537 Non- ionic OTG 0.031-<0.5%  >=0.5%  9 308.4 Non- ionic Group 2 Genapol 0.001-0.5%    >0.5%    / 627 Non- C-100 ionic Tween 20 0.001-0.5%    >0.5%    0.059 1228 Non- ionic Tween 80 0.001-0.25%    >0.25%    0.012 1310 Non- ionic Group 3 Deoxycholic /  >=0.0004% 1.5 414.6 Ionic Acid SDS /  >=0.0004% 2.3 288.5 Ionic

[0132] The enhancing/inhibiting effect of Zwittergent 3-14 was also tested using purified Limulus factor C (FIG. 6). A similar enhancing/inhibiting effect was observed, although the relative factor C activity ratio, the enhancing and inhibiting detergent concentrations were different from those in the recombinant Factor C assay.

EXAMPLE 11

[0133] Antisera Against Limulus Factor C

[0134] We isolated the factor C from Limulus and generated antisera against the protein. The Limulus lysate was first separated with a S-100 gel filtration followed by cation-ion exchange column. The fractions were assayed for factor C activity using the N-t-BOC-Val-Pro-Arg 7-Amido-4-methyl coumarin substrate. The Limulus factor C was purified 73 fold with 80% homogeneity as determined by enzyme assay and SDS-PAGE. The molecular weight of Limulus factor C was 117 kDa by SDS-PAGE under non-reducing conditions. Reduced SDS-PAGE showed two major bands of 79 kDa and 40 kDa, corresponding to the heavy and light chain. Tryptic peptide sequencing revealed that the Limulus factor C sequence closely matched the Asian species, with >90% sequence identity. A specific polyclonal antibody against the Limulus factor C was generated in rabbits. The anti-factor C purified IgG inhibited the activation of factor C by LPS but had no effect on the protease activity once the factor C was activated by LPS. The factor C antisera demonstrated the importance of this protein in the initial recognition of LPS by Limulus lysate.

EXAMPLE 12

[0135] Increase in Sensitivity in Endotoxin Detection in the Presence of Surfactant

[0136] A one-step, 1-hour endpoint assay was performed. Endotoxin O55:B5, 0.01, 0.1, 1, and 10 EU/ml were used for the standard curve. Blank and endotoxin standards (100 μl each) were added to a 96-well plate. Recombinant Factor C supernatant, assay buffer (150 mM NaCl, 150 mM Tris, pH 8.0, and 1.5% lactose, with or without 0.0125% Zwittergent) and substrate solution (0.2 mM in water) were mixed at 1:4:5 ratios. This mixture was added into each blank and endotoxin standard. The fluorescence was recorded at time zero and time 1 hour. The difference in fluorescences (delta fluorescence) were normalized with the blank. Normalized delta fluorescence was then graphed against endotoxin concentration in a log-log scale. Each data point is the result of duplicate assays.

[0137] The results are shown in FIG. 7. The endotoxin detection sensitivity increased 10-fold when surfactant was included.

EXAMPLE 13

[0138] One-Step Endotoxin Assay

[0139] A one-step endotoxin assay can be carried out in a 96-well plate, using 100 μl each of blank and endotoxin standards. One hundred microliters of a mixture of recombinant Factor C supernatant (Baculovirus-infected Sf9 cell culture medium), buffer (150 mM Tri, pH 8.0, 150 mM NaCl, 1.5% beta-lactose, and 0.0125% Zwittergent 3-14) and fluorogenic substrate (DPR-coumarin, 0.2 mM) at a ratio of 1:4:5 is added to wells of the plate. The plate is incubated at 37° C. for 1 hour. Excitation and emission are read at 390 and 440 nm, respectively, in a fluorescence microplate reader.

[0140] The results of a one-step recombinant Factor C endotoxin assay are shown in FIG. 8.

1 8 1 1906 DNA Tachypleudus tridentata 1 gtaagtatca tcaggtttaa cgcgaacgtg gaagaactct gaaggtaact taagtatggt 60 cttagcgtcg tttttggtgt ctggtttagt tctagggata ctagcccaac aaatgcgtcc 120 agttcagtcc agaggagtag atctgggctt gtgtgatgaa acgaggttcg agtgtaagtg 180 tggagatcca ggctatgtgt tcaacgtccc tatgaaacaa tgcacgtact tctatcgatg 240 gaggccttat tgtaaaccat gtgatgacct ggaggctaag gacatttgtc caaagtacaa 300 acgatgtcaa gagtgtaagg ctggtcttga tagttgtgtt acttgtccac ctaacaaata 360 tggtacttgg tgtagcggtg aatgtcaatg taagaatgga ggtatctgtg accagaggac 420 aggagcttgt acctgtcgtg acagatatga aggagcgcac tgtgaaattc tcaaaggttg 480 tcctcttctt ccatcggatt ctcaagttca ggaagtcaga aacccaccag ataatcccca 540 aactattgac tacagctgtt caccagggtt caagcttaaa ggcgtggcac gaattagctg 600 tctcccaaat ggacagtgga gtagctttcc acccaaatgt attcgagaat gtgccaaggt 660 ttcatctcca gaacacggga aagtgaatgc tcctagtggc aatatgatag aaggggctac 720 tttacggttc tcatgtgata gtccctacta cttgattggt caagaaacat taacctgcca 780 gggtaatggt cagtggagtg gacaaatacc acaatgtaag aagttggtct tctgtcctga 840 ccttgatcct gtaaaccatg ctgaacacca ggttaaaatt ggtgtggaac aaaaatatgg 900 tcagtttcct caaggcactg aagtgaccta tacgtgttcg ggtaactact tcttgatggg 960 ttttaacacc ttaaaatgta accctgatgg gtcctggtca ggatcacagc catcctgtgt 1020 taaagtggca gacagagagg tcgactgtga cagtaaagct gtagacttct tggatgatgt 1080 tggtgaacct gtcaggatcc actgtcctgc tggctgttct ttgacagctg gtactgtgtg 1140 gggtacagcc atataccacg aactttcctc agtgtgtcgt gcagccatcc atgctggcaa 1200 gcttccaaac tctggagggg cggtgcatgt agtgaacaat ggcccctact cggactttct 1260 gggtagtgac ctgaatggga taaaatcgga agagttgaag tctcttgccc gcagttttcg 1320 atttgattat gtcagttcat ccacagcagg tagatcagga tgtcctgatg gatggtttga 1380 ggtagaagag aactgtgtgt acgttacatc aaaacagaga gcctgggaaa gagctcaagg 1440 tgtgtgtacc aatatggctg ctcgtcttgc tgtgctagac aaagatctaa ttccgagttc 1500 cttgactgag actctacgag ggaaaggtac tgataatgtt actgcaacct aagtagactt 1560 tattttagtc taagatatct tgtgtcaatt gttgacttgc tactcttact ttattgtaat 1620 aaaactgtta taaagtatta agtcttgttt attttattac tgtttaaagt atactacaag 1680 ggttacacct aaaaggaaat ttctatctga caatttcata aaaagtggat gttacttttg 1740 attttcgttg gttgttaaat gcacatccgg tttgtaaaca tctaagttcc cacaaacagg 1800 ctctgtggtc ttgtaaaaat ctaaactaat accactttta atatgtttta aacctttttt 1860 ttatgtatgc ttatcagaga ctaaaataaa ggtttttaat aactgt 1906 2 498 PRT Tachypleudus tridentata 2 Met Val Leu Ala Ser Phe Leu Val Ser Gly Leu Val Leu Gly Ile Leu 1 5 10 15 Ala Gln Gln Met Arg Pro Val Gln Ser Arg Gly Val Asp Leu Gly Leu 20 25 30 Cys Asp Glu Thr Arg Phe Glu Cys Lys Cys Gly Asp Pro Gly Tyr Val 35 40 45 Phe Asn Val Pro Met Lys Gln Cys Thr Tyr Phe Tyr Arg Trp Arg Pro 50 55 60 Tyr Cys Lys Pro Cys Asp Asp Leu Glu Ala Lys Asp Ile Cys Pro Lys 65 70 75 80 Tyr Lys Arg Cys Gln Glu Cys Lys Ala Gly Leu Asp Ser Cys Val Thr 85 90 95 Cys Pro Pro Asn Lys Tyr Gly Thr Trp Cys Ser Gly Glu Cys Gln Cys 100 105 110 Lys Asn Gly Gly Ile Cys Asp Gln Arg Thr Gly Ala Cys Thr Cys Arg 115 120 125 Asp Arg Tyr Glu Gly Ala His Cys Glu Ile Leu Lys Gly Cys Pro Leu 130 135 140 Leu Pro Ser Asp Ser Gln Val Gln Glu Val Arg Asn Pro Pro Asp Asn 145 150 155 160 Pro Gln Thr Ile Asp Tyr Ser Cys Ser Pro Gly Phe Lys Leu Lys Gly 165 170 175 Val Ala Arg Ile Ser Cys Leu Pro Asn Gly Gln Trp Ser Ser Phe Pro 180 185 190 Pro Lys Cys Ile Arg Glu Cys Ala Lys Val Ser Ser Pro Glu His Gly 195 200 205 Lys Val Asn Ala Pro Ser Gly Asn Met Ile Glu Gly Ala Thr Leu Arg 210 215 220 Phe Ser Cys Asp Ser Pro Tyr Tyr Leu Ile Gly Gln Glu Thr Leu Thr 225 230 235 240 Cys Gln Gly Asn Gly Gln Trp Ser Gly Gln Ile Pro Gln Cys Lys Lys 245 250 255 Leu Val Phe Cys Pro Asp Leu Asp Pro Val Asn His Ala Glu His Gln 260 265 270 Val Lys Ile Gly Val Glu Gln Lys Tyr Gly Gln Phe Pro Gln Gly Thr 275 280 285 Glu Val Thr Tyr Thr Cys Ser Gly Asn Tyr Phe Leu Met Gly Phe Asn 290 295 300 Thr Leu Lys Cys Asn Pro Asp Gly Ser Trp Ser Gly Ser Gln Pro Ser 305 310 315 320 Cys Val Lys Val Ala Asp Arg Glu Val Asp Cys Asp Ser Lys Ala Val 325 330 335 Asp Phe Leu Asp Asp Val Gly Glu Pro Val Arg Ile His Cys Pro Ala 340 345 350 Gly Cys Ser Leu Thr Ala Gly Thr Val Trp Gly Thr Ala Ile Tyr His 355 360 365 Glu Leu Ser Ser Val Cys Arg Ala Ala Ile His Ala Gly Lys Leu Pro 370 375 380 Asn Ser Gly Gly Ala Val His Val Val Asn Asn Gly Pro Tyr Ser Asp 385 390 395 400 Phe Leu Gly Ser Asp Leu Asn Gly Ile Lys Ser Glu Glu Leu Lys Ser 405 410 415 Leu Ala Arg Ser Phe Arg Phe Asp Tyr Val Ser Ser Ser Thr Ala Gly 420 425 430 Arg Ser Gly Cys Pro Asp Gly Trp Phe Glu Val Glu Glu Asn Cys Val 435 440 445 Tyr Val Thr Ser Lys Gln Arg Ala Trp Glu Arg Ala Gln Gly Val Cys 450 455 460 Thr Asn Met Ala Ala Arg Leu Ala Val Leu Asp Lys Asp Leu Ile Pro 465 470 475 480 Ser Ser Leu Thr Glu Thr Leu Arg Gly Lys Gly Thr Asp Asn Val Thr 485 490 495 Ala Thr 3 3467 DNA Tachypleudus tridentata 3 caggtttaac gcgaacgtgg aagaactctg aaggtaactt aagtatggtc ttagcgtcgt 60 ttttggtgtc tggtttagtt ctagggatac tagcccaaca aatgcgtcca gttcagtcca 120 gaggagtaga tctgggcttg tgtgatgaaa cgaggttcga gtgtaagtgt ggagatccag 180 gctatgtgtt caacgtccct atgaaacaat gcacgtactt ctatcgatgg aggccttatt 240 gtaaaccatg tgatgacctg gaggctaagg acatttgtcc aaagtacaaa cgatgtcaag 300 agtgtaaggc tggtcttgat agttgtgtta cttgtccacc taacaaatat ggtacttggt 360 gtagcggtga atgtcaatgt aagaatggag gtatctgtga ccagaggaca ggagcttgta 420 cctgtcgtga cagatatgaa ggagcgcact gtgaaattct caaaggttgt cctcttcttc 480 catcggattc tcaagttcag gaagtcagaa acccaccaga taatccccaa actattgact 540 acagctgttc accagggttc aagcttaaag gcgtggcacg aattagctgt ctcccaaatg 600 gacagtggag tagctttcca cccaaatgta ttcgagaatg tgccaaggtt tcatctccag 660 aacacgggaa agtgaatgct cctagtggca atatgataga aggggctact ttacggttct 720 catgtgatag tccctactac ttgattggtc aagaaacatt aacctgccag ggtaatggtc 780 agtggagtgg acaaatacca caatgtaaga agttggtctt ctgtcctgac cttgatcctg 840 taaaccatgc tgaacaccag gttaaaattg gtgtggaaca aaaatatggt cagtttcctc 900 aaggcactga agtgacctat acgtgttcgg gtaactactt cttgatgggt tttaacacct 960 taaaatgtaa ccctgatggg tcctggtcag gatcacagcc atcctgtgtt aaagtggcag 1020 acagagaggt cgactgtgac agtaaagctg tagacttctt ggatgatgtt ggtgaacctg 1080 tcaggatcca ctgtcctgct ggctgttctt tgacagctgg tactgtgtgg ggtacagcca 1140 tataccacga actttcctca gtgtgtcgtg cagccatcca tgctggcaag cttccaaact 1200 ctggaggggc ggtgcatgta gtgaacaatg gcccctactc ggactttctg ggtagtgacc 1260 tgaatgggat aaaatcggaa gagttgaagt ctcttgcccg cagttttcga tttgattatg 1320 tcagttcatc cacagcaggt agatcaggat gtcctgatgg atggtttgag gtagaagaga 1380 actgtgtgta cgttacatca aaacagagag cctgggaaag agctcaaggt gtgtgtacca 1440 atatggctgc tcgtcttgct gtgctagaca aagatctaat tccgagttcc ttgactgaga 1500 ctctacgagg gaaagggtta acaaccacat ggataggatt gcacagacta gatgctgaga 1560 agccctttgt ttgggagcta atggatcgta gtaatgtggt tctgaatgat aacctaacat 1620 tctgggcctc tggcgaacct ggaaatgaaa ctaactgtgt atatctggac atccgagatc 1680 agctgcagcc tgtgtggaaa accaagtcat gttttcagcc ctcaagcttt gcttgcatga 1740 tggatttgtc agacagaaat aaagccaaat gcgatgaccc tggaccactg gaaaatggac 1800 acgccacact tcatggacaa agtattgatg ggttctatgc tggttcttct ataaggtaca 1860 gctgtgaggt tctccactac ctcagtggaa ctgagaccgt aacttgtaca acaaatggca 1920 catggagtgc tcctaaacct cgatgtatca aagtcatcac ctgccaaaac cctcctgtac 1980 catcatatgg ttctgtggaa atcaaacccc caagtcggac aaactcgatc agtcgtgttg 2040 ggtcaccttt cttgaggttg ccacggttac ccctcccatt agccagagca gccaaacctc 2100 ctccaaaacc tagatcctca caaccctcta ctgtggactt ggcttctaaa gttaaactac 2160 ctgaaggtca ttaccgggta gggtctcgag ccatttacac gtgcgagtcg agatactacg 2220 aactacttgg atctcaaggc agaagatgtg actctaatgg aaactggagt ggtcggcccg 2280 ctagctgtat tccagtttgt ggacggtcag actctcctcg ttctcctttc atctggaatg 2340 ggaattctac agaaataggt cagtggccgt ggcaggcagg aatctctcga tggcttgcag 2400 accacaatat gtggtttctc cagtgtggag gatccctatt gaatgagaaa tggatcgtca 2460 ctgctgccca ctgtgtcacc tactctgcta ctgctgagat aattgatccc agtcagttta 2520 aaatctatct gggcaagtac taccgtgatg acagtagaga cgatgactac gtacaagtaa 2580 gagaggctct cgagatccac gtaaatccta actacgaccc cggcaatctc aactttgaca 2640 tagccctaat tcaactgaaa actcctgtta ctttgacaac acgagtccaa ccaatctgtc 2700 tgcctactga catcacaaca agagaacact tgaaggaggg aacattagca gtggtgacag 2760 gttggggttt gaatgaaaac aacacatatt cagagatgat tcaacaagct gtgctacctg 2820 ttgttgcagc aagcacctgt gaagaggggt acaaggaagc agacttacca ctgacagtaa 2880 cagagaacat gttctgtgca ggttacaaga agggacgtta tgatgcctgc agtggggaca 2940 gtggaggacc attagtgttt gctgatgatt cccgtaccga aaggcggtgg gtcttggaag 3000 ggattgtcag ctggggcagt cccagtggat gtggcaaggc taaccagtat gggggcttca 3060 ctaaagttaa cgtttttcta tcatggatta ggcagttcat ttgaaactga tctaaatatt 3120 ttaatcatgg ttataaacgt cttgtttcct atttttgctt tactagttta acccataaga 3180 aggttaagtg ggtaaggcac cagtgtcatt gtttgtttgt ttttacaaat ggttcgttta 3240 gtcaatgaat gagaatagta tccattggac actgttacct tttatgtttt tattctacct 3300 ttttatatta ccatgcaagt atttggaata tcttctatac atatgaaaat tctgttattt 3360 ttccataaag ttggtttctg gtgtgcgtta agtccaccac tggagaatga tgtaattttc 3420 actagtacat gaaataaata tagaacaaat ctattataaa ctacctt 3467 4 1019 PRT Tachypleudus tridentata 4 Met Val Leu Ala Ser Phe Leu Val Ser Gly Leu Val Leu Gly Ile Leu 1 5 10 15 Ala Gln Gln Met Arg Pro Val Gln Ser Arg Gly Val Asp Leu Gly Leu 20 25 30 Cys Asp Glu Thr Arg Phe Glu Cys Lys Cys Gly Asp Pro Gly Tyr Val 35 40 45 Phe Asn Val Pro Met Lys Gln Cys Thr Tyr Phe Tyr Arg Trp Arg Pro 50 55 60 Tyr Cys Lys Pro Cys Asp Asp Leu Glu Ala Lys Asp Ile Cys Pro Lys 65 70 75 80 Tyr Lys Arg Cys Gln Glu Cys Lys Ala Gly Leu Asp Ser Cys Val Thr 85 90 95 Cys Pro Pro Asn Lys Tyr Gly Thr Trp Cys Ser Gly Glu Cys Gln Cys 100 105 110 Lys Asn Gly Gly Ile Cys Asp Gln Arg Thr Gly Ala Cys Thr Cys Arg 115 120 125 Asp Arg Tyr Glu Gly Ala His Cys Glu Ile Leu Lys Gly Cys Pro Leu 130 135 140 Leu Pro Ser Asp Ser Gln Val Gln Glu Val Arg Asn Pro Pro Asp Asn 145 150 155 160 Pro Gln Thr Ile Asp Tyr Ser Cys Ser Pro Gly Phe Lys Leu Lys Gly 165 170 175 Val Ala Arg Ile Ser Cys Leu Pro Asn Gly Gln Trp Ser Ser Phe Pro 180 185 190 Pro Lys Cys Ile Arg Glu Cys Ala Lys Val Ser Ser Pro Glu His Gly 195 200 205 Lys Val Asn Ala Pro Ser Gly Asn Met Ile Glu Gly Ala Thr Leu Arg 210 215 220 Phe Ser Cys Asp Ser Pro Tyr Tyr Leu Ile Gly Gln Glu Thr Leu Thr 225 230 235 240 Cys Gln Gly Asn Gly Gln Trp Ser Gly Gln Ile Pro Gln Cys Lys Lys 245 250 255 Leu Val Phe Cys Pro Asp Leu Asp Pro Val Asn His Ala Glu His Gln 260 265 270 Val Lys Ile Gly Val Glu Gln Lys Tyr Gly Gln Phe Pro Gln Gly Thr 275 280 285 Glu Val Thr Tyr Thr Cys Ser Gly Asn Tyr Phe Leu Met Gly Phe Asn 290 295 300 Thr Leu Lys Cys Asn Pro Asp Gly Ser Trp Ser Gly Ser Gln Pro Ser 305 310 315 320 Cys Val Lys Val Ala Asp Arg Glu Val Asp Cys Asp Ser Lys Ala Val 325 330 335 Asp Phe Leu Asp Asp Val Gly Glu Pro Val Arg Ile His Cys Pro Ala 340 345 350 Gly Cys Ser Leu Thr Ala Gly Thr Val Trp Gly Thr Ala Ile Tyr His 355 360 365 Glu Leu Ser Ser Val Cys Arg Ala Ala Ile His Ala Gly Lys Leu Pro 370 375 380 Asn Ser Gly Gly Ala Val His Val Val Asn Asn Gly Pro Tyr Ser Asp 385 390 395 400 Phe Leu Gly Ser Asp Leu Asn Gly Ile Lys Ser Glu Glu Leu Lys Ser 405 410 415 Leu Ala Arg Ser Phe Arg Phe Asp Tyr Val Ser Ser Ser Thr Ala Gly 420 425 430 Arg Ser Gly Cys Pro Asp Gly Trp Phe Glu Val Glu Glu Asn Cys Val 435 440 445 Tyr Val Thr Ser Lys Gln Arg Ala Trp Glu Arg Ala Gln Gly Val Cys 450 455 460 Thr Asn Met Ala Ala Arg Leu Ala Val Leu Asp Lys Asp Leu Ile Pro 465 470 475 480 Ser Ser Leu Thr Glu Thr Leu Arg Gly Lys Gly Leu Thr Thr Thr Trp 485 490 495 Ile Gly Leu His Arg Leu Asp Ala Glu Lys Pro Phe Val Trp Glu Leu 500 505 510 Met Asp Arg Ser Asn Val Val Leu Asn Asp Asn Leu Thr Phe Trp Ala 515 520 525 Ser Gly Glu Pro Gly Asn Glu Thr Asn Cys Val Tyr Leu Asp Ile Arg 530 535 540 Asp Gln Leu Gln Pro Val Trp Lys Thr Lys Ser Cys Phe Gln Pro Ser 545 550 555 560 Ser Phe Ala Cys Met Met Asp Leu Ser Asp Arg Asn Lys Ala Lys Cys 565 570 575 Asp Asp Pro Gly Pro Leu Glu Asn Gly His Ala Thr Leu His Gly Gln 580 585 590 Ser Ile Asp Gly Phe Tyr Ala Gly Ser Ser Ile Arg Tyr Ser Cys Glu 595 600 605 Val Leu His Tyr Leu Ser Gly Thr Glu Thr Val Thr Cys Thr Thr Asn 610 615 620 Gly Thr Trp Ser Ala Pro Lys Pro Arg Cys Ile Lys Val Ile Thr Cys 625 630 635 640 Gln Asn Pro Pro Val Pro Ser Tyr Gly Ser Val Glu Ile Lys Pro Pro 645 650 655 Ser Arg Thr Asn Ser Ile Ser Arg Val Gly Ser Pro Phe Leu Arg Leu 660 665 670 Pro Arg Leu Pro Leu Pro Leu Ala Arg Ala Ala Lys Pro Pro Pro Lys 675 680 685 Pro Arg Ser Ser Gln Pro Ser Thr Val Asp Leu Ala Ser Lys Val Lys 690 695 700 Leu Pro Glu Gly His Tyr Arg Val Gly Ser Arg Ala Ile Tyr Thr Cys 705 710 715 720 Glu Ser Arg Tyr Tyr Glu Leu Leu Gly Ser Gln Gly Arg Arg Cys Asp 725 730 735 Ser Asn Gly Asn Trp Ser Gly Arg Pro Ala Ser Cys Ile Pro Val Cys 740 745 750 Gly Arg Ser Asp Ser Pro Arg Ser Pro Phe Ile Trp Asn Gly Asn Ser 755 760 765 Thr Glu Ile Gly Gln Trp Pro Trp Gln Ala Gly Ile Ser Arg Trp Leu 770 775 780 Ala Asp His Asn Met Trp Phe Leu Gln Cys Gly Gly Ser Leu Leu Asn 785 790 795 800 Glu Lys Trp Ile Val Thr Ala Ala His Cys Val Thr Tyr Ser Ala Thr 805 810 815 Ala Glu Ile Ile Asp Pro Ser Gln Phe Lys Ile Tyr Leu Gly Lys Tyr 820 825 830 Tyr Arg Asp Asp Ser Arg Asp Asp Asp Tyr Val Gln Val Arg Glu Ala 835 840 845 Leu Glu Ile His Val Asn Pro Asn Tyr Asp Pro Gly Asn Leu Asn Phe 850 855 860 Asp Ile Ala Leu Ile Gln Leu Lys Thr Pro Val Thr Leu Thr Thr Arg 865 870 875 880 Val Gln Pro Ile Cys Leu Pro Thr Asp Ile Thr Thr Arg Glu His Leu 885 890 895 Lys Glu Gly Thr Leu Ala Val Val Thr Gly Trp Gly Leu Asn Glu Asn 900 905 910 Asn Thr Tyr Ser Glu Met Ile Gln Gln Ala Val Leu Pro Val Val Ala 915 920 925 Ala Ser Thr Cys Glu Glu Gly Tyr Lys Glu Ala Asp Leu Pro Leu Thr 930 935 940 Val Thr Glu Asn Met Phe Cys Ala Gly Tyr Lys Lys Gly Arg Tyr Asp 945 950 955 960 Ala Cys Ser Gly Asp Ser Gly Gly Pro Leu Val Phe Ala Asp Asp Ser 965 970 975 Arg Thr Glu Arg Arg Trp Val Leu Glu Gly Ile Val Ser Trp Gly Ser 980 985 990 Pro Ser Gly Cys Gly Lys Ala Asn Gln Tyr Gly Gly Phe Thr Lys Val 995 1000 1005 Asn Val Phe Leu Ser Trp Ile Arg Gln Phe Ile 1010 1015 5 4182 DNA Carcinoscorpius rotundicauda 5 gtatttaatg tctcaacggt aaaggtttca ttgtagctaa tatttaactt cctccctgtg 60 ccccaaatcg cgagtatgac gtcagttaag acttcgtatt ttaagagtta aacacgagcc 120 ttaaagagcg atattttttt tgttaaacac ttccaactta atacaattgg caaactttca 180 aaaataaagt ggaaaaggag gtaaaaaaga tgaaaaaaat tcgcatacaa tagaatacaa 240 taaaatgtgt tgtctttact gtcaacactt actgttcgtt cggtcacagc tgtgaatcgg 300 ggtgacttta tgtttgtagt ggtcttaaaa acgggtactt ggttgttttg aaaattttaa 360 aacctacata tgattctcct aaaattttgt ttataaatta gcaccatttg cgacctaaat 420 cttttttgta gtcttaagtt tagttgacat aaaaacaaaa tttgtaacaa cacacggtat 480 aaactaaata gcttcagatg ggtcgtatga caaggaaact tttaaataat tatgaaagtt 540 tttttaaaat ttgactaagg tttagattat gtgggtgaca tgcttcgaca cgtttctttt 600 tgtttgtgaa agttcagttt tctgtttgtt gtgtgtgtgg aggtttggtt tctgtaggtg 660 gcgtgttttc tacagttttc cattcgttaa gtcaacagtt gttttattac agtgttacca 720 ttactctctc cacaatacct caaagttcta ctctgtgaat cctgacaagc cagagtacat 780 tctttcaggt ttagttctag ggctactagc ccaaaaaatg cgcccagttc agtccaaagg 840 agtagatcta ggcttgtgtg atgaaacgag gttcgagtgt aagtgtggcg atccaggcta 900 tgtgttcaac attccagtga aacaatgtac atacttttat cgatggaggc cgtattgtaa 960 accatgtgat gacctggagg ctaaggatat ttgtccaaag tacaaacgat gtcaagagtg 1020 taaggctggt cttgatagtt gtgttacttg tccacctaac aaatatggta cttggtgtag 1080 cggtgaatgt cagtgtaaga atggaggtat ctgtgaccag aggacaggag cttgtgcatg 1140 tcgtgacaga tatgaagggg tgcactgtga aattctcaaa ggttgtcctc ttcttccatc 1200 ggattctcag gttcaggaag tcagaaatcc accagataat ccccaaacta ttgactacag 1260 ctgttcacca gggttcaagc ttaagggtat ggcacgaatt agctgtctcc caaatggaca 1320 gtggagtaac tttccaccca aatgtattcg agaatgtgcc atggtttcat ctccagaaca 1380 tgggaaagtg aatgctctta gtggtgatat gatagaaggg gctactttac ggttctcatg 1440 tgatagtccc tactacttga ttggtcaaga aacattaacc tgtcagggta atggtcagtg 1500 gaatggacag ataccacaat gtaagaactt agtcttctgt cctgacctgg atcctgtaaa 1560 ccatgctgaa cacaaggtta aaattggtgt ggaacaaaaa tatggtcagt ttcctcaagg 1620 cactgaagtg acctatacgt gttcgggtaa ctacttcttg atgggttttg acaccttaaa 1680 atgtaaccct gatgggtctt ggtcaggatc acagccatcc tgtgttaaag tggcagacag 1740 agaggtcgac tgtgacagta aagctgtaga cttcttggat gatgttggtg aacctgtcag 1800 gatccactgt cctgctggct gttctttgac agctggtact gtgtggggta cagccatata 1860 ccatgaactt tcctcagtgt gtcgtgcagc catccatgct ggcaagcttc caaactctgg 1920 aggagcggtg catgttgtga acaatggccc ctactcggac tttctgggta gtgacctgaa 1980 tgggataaaa tccgaagagt tgaagtctct tgcccggagt ttccgattcg attatgtcag 2040 ttcctccaca gcaggtaaat caggatgtcc tgatggatgg tttgaggtag acgagaactg 2100 tgtgtacgtt acatcaaaac agagagcctg ggaaagagct caaggtgtgt gtaccaatat 2160 ggctgctcgt cttgctgtgc tggacaaaga tgtaattcca aattcattga ctgagactct 2220 acgagggaaa gggttaacaa ccacgtggat aggattgcac agactagatg ctgagaagcc 2280 ctttatttgg gagttaatgg atcgtagtaa tgtggttctg aatgataacc taacattctg 2340 ggcctctggc gaacctggaa atgaaactaa ctgtgtatat atggacatcc aagatcagtt 2400 gcagtctgtg tggaaaacca agtcatgttt tcagccctca agttttgctt gcatgatgga 2460 tctgtcagac agaaataaag ccaaatgcga tgatcctgga tcactggaaa atggacacgc 2520 cacacttcat ggacaaagta ttgatgggtt ctatgctggt tcttctataa ggtacagctg 2580 tgaggttctc cactacctca gtggaactga aaccgtaact tgtacaacaa atggcacatg 2640 gagtgctcct aaacctcgat gtatcaaagt catcacctgc caaaaccccc ctgtaccatc 2700 atatggttct gtggaaatca aacccccaag tcggacaaac tcgataagtc gtgttgggtc 2760 acctttcttg aggttgccac ggttacccct cccattagcc agagcagcca aacctcctcc 2820 aaaacctaga tcctcacaac cctctactgt ggacttggct tctaaagtta aactacctga 2880 aggtcattac cgggtagggt ctcgagccat ttacacgtgc gagtcgagat actacgaact 2940 acttggatct caaggcagaa gatgtgactc taatggaaac tggagtggtc ggccagcgag 3000 ctgtattcca gtttgtggac ggtcagactc tcctcgttct ccttttatct ggaatgggaa 3060 ttctacagaa ataggtcagt ggccgtggca ggcaggaatc tctagatggc ttgcagacca 3120 caatatgtgg tttctccagt gtggaggatc tctattgaat gagaaatgga tcgtcactgc 3180 tgcccactgt gtcacctact ctgctactgc tgagattatt gaccccaatc agtttaaaat 3240 gtatctgggc aagtactacc gtgatgacag tagagacgat gactatgtac aagtaagaga 3300 ggctcttgag atccacgtga atcctaacta cgaccccggc aatctcaact ttgacatagc 3360 cctaattcaa ctgaaaactc ctgttacttt gacaacacga gtccaaccaa tctgtctgcc 3420 tactgacatc acaacaagag aacacttgaa ggagggaaca ttagcagtgg tgacaggttg 3480 gggtttgaat gaaaacaaca cctattcaga gacgattcaa caagctgtgc tacctgttgt 3540 tgcagccagc acctgtgaag aggggtacaa ggaagcagac ttaccactga cagtaacaga 3600 gaacatgttc tgtgcaggtt acaagaaggg acgttatgat gcctgcagtg gggacagtgg 3660 aggaccttta gtgtttgctg atgattcccg taccgaaagg cggtgggtct tggaagggat 3720 tgtcagctgg ggcagtccca gtggatgtgg caaggcgaac cagtacgggg gcttcactaa 3780 agttaacgtt ttcctgtcat ggattaggca gttcatttga aactgatcta aatattttaa 3840 gcatggttat aaacgtcttg ttcctattat tgctttactg gtttaaccca taagaaggtt 3900 aacggggtaa ggcacaagga tcattgtttc tgtttgtttt tacaaatggt tcttttagtc 3960 agtgaatgag aatagtatcc attggagact gttacctttt attctacctt tttatattac 4020 tatgcaagta tttgggatat cttctacaca tgaaaattct gtcattttac cataaatttg 4080 gtttctggtg tgtgtgttaa gtccaccact agagaacgat gtaattttca atagtacatg 4140 aaataaatat agaacaaatc tattataaaa aaaaaaaaaa aa 4182 6 1083 PRT Carcinoscorpius rotundicauda 6 Met Trp Val Thr Cys Phe Asp Thr Phe Leu Phe Val Cys Glu Ser Ser 1 5 10 15 Val Phe Cys Leu Leu Cys Val Trp Arg Phe Gly Phe Cys Arg Trp Arg 20 25 30 Val Phe Tyr Ser Phe Pro Phe Val Lys Ser Thr Val Val Leu Leu Gln 35 40 45 Cys Tyr His Tyr Ser Leu His Asn Thr Ser Lys Phe Tyr Ser Val Asn 50 55 60 Pro Asp Lys Pro Glu Tyr Ile Leu Ser Gly Leu Val Leu Gly Leu Leu 65 70 75 80 Ala Gln Lys Met Arg Pro Val Gln Ser Lys Gly Val Asp Leu Gly Leu 85 90 95 Cys Asp Glu Thr Arg Phe Glu Cys Lys Cys Gly Asp Pro Gly Tyr Val 100 105 110 Phe Asn Ile Pro Val Lys Gln Cys Thr Tyr Phe Tyr Arg Trp Arg Pro 115 120 125 Tyr Cys Lys Pro Cys Asp Asp Leu Glu Ala Lys Asp Ile Cys Pro Lys 130 135 140 Tyr Lys Arg Cys Gln Glu Cys Lys Ala Gly Leu Asp Ser Cys Val Thr 145 150 155 160 Cys Pro Pro Asn Lys Tyr Gly Thr Trp Cys Ser Gly Glu Cys Gln Cys 165 170 175 Lys Asn Gly Gly Ile Cys Asp Gln Arg Thr Gly Ala Cys Ala Cys Arg 180 185 190 Asp Arg Tyr Glu Gly Val His Cys Glu Ile Leu Lys Gly Cys Pro Leu 195 200 205 Leu Pro Ser Asp Ser Gln Val Gln Glu Val Arg Asn Pro Pro Asp Asn 210 215 220 Pro Gln Thr Ile Asp Tyr Ser Cys Ser Pro Gly Phe Lys Leu Lys Gly 225 230 235 240 Met Ala Arg Ile Ser Cys Leu Pro Asn Gly Gln Trp Ser Asn Phe Pro 245 250 255 Pro Lys Cys Ile Arg Glu Cys Ala Met Val Ser Ser Pro Glu His Gly 260 265 270 Lys Val Asn Ala Leu Ser Gly Asp Met Ile Glu Gly Ala Thr Leu Arg 275 280 285 Phe Ser Cys Asp Ser Pro Tyr Tyr Leu Ile Gly Gln Glu Thr Leu Thr 290 295 300 Cys Gln Gly Asn Gly Gln Trp Asn Gly Gln Ile Pro Gln Cys Lys Asn 305 310 315 320 Leu Val Phe Cys Pro Asp Leu Asp Pro Val Asn His Ala Glu His Lys 325 330 335 Val Lys Ile Gly Val Glu Gln Lys Tyr Gly Gln Phe Pro Gln Gly Thr 340 345 350 Glu Val Thr Tyr Thr Cys Ser Gly Asn Tyr Phe Leu Met Gly Phe Asp 355 360 365 Thr Leu Lys Cys Asn Pro Asp Gly Ser Trp Ser Gly Ser Gln Pro Ser 370 375 380 Cys Val Lys Val Ala Asp Arg Glu Val Asp Cys Asp Ser Lys Ala Val 385 390 395 400 Asp Phe Leu Asp Asp Val Gly Glu Pro Val Arg Ile His Cys Pro Ala 405 410 415 Gly Cys Ser Leu Thr Ala Gly Thr Val Trp Gly Thr Ala Ile Tyr His 420 425 430 Glu Leu Ser Ser Val Cys Arg Ala Ala Ile His Ala Gly Lys Leu Pro 435 440 445 Asn Ser Gly Gly Ala Val His Val Val Asn Asn Gly Pro Tyr Ser Asp 450 455 460 Phe Leu Gly Ser Asp Leu Asn Gly Ile Lys Ser Glu Glu Leu Lys Ser 465 470 475 480 Leu Ala Arg Ser Phe Arg Phe Asp Tyr Val Ser Ser Ser Thr Ala Gly 485 490 495 Lys Ser Gly Cys Pro Asp Gly Trp Phe Glu Val Asp Glu Asn Cys Val 500 505 510 Tyr Val Thr Ser Lys Gln Arg Ala Trp Glu Arg Ala Gln Gly Val Cys 515 520 525 Thr Asn Met Ala Ala Arg Leu Ala Val Leu Asp Lys Asp Val Ile Pro 530 535 540 Asn Ser Leu Thr Glu Thr Leu Arg Gly Lys Gly Leu Thr Thr Thr Trp 545 550 555 560 Ile Gly Leu His Arg Leu Asp Ala Glu Lys Pro Phe Ile Trp Glu Leu 565 570 575 Met Asp Arg Ser Asn Val Val Leu Asn Asp Asn Leu Thr Phe Trp Ala 580 585 590 Ser Gly Glu Pro Gly Asn Glu Thr Asn Cys Val Tyr Met Asp Ile Gln 595 600 605 Asp Gln Leu Gln Ser Val Trp Lys Thr Lys Ser Cys Phe Gln Pro Ser 610 615 620 Ser Phe Ala Cys Met Met Asp Leu Ser Asp Arg Asn Lys Ala Lys Cys 625 630 635 640 Asp Asp Pro Gly Ser Leu Glu Asn Gly His Ala Thr Leu His Gly Gln 645 650 655 Ser Ile Asp Gly Phe Tyr Ala Gly Ser Ser Ile Arg Tyr Ser Cys Glu 660 665 670 Val Leu His Tyr Leu Ser Gly Thr Glu Thr Val Thr Cys Thr Thr Asn 675 680 685 Gly Thr Trp Ser Ala Pro Lys Pro Arg Cys Ile Lys Val Ile Thr Cys 690 695 700 Gln Asn Pro Pro Val Pro Ser Tyr Gly Ser Val Glu Ile Lys Pro Pro 705 710 715 720 Ser Arg Thr Asn Ser Ile Ser Arg Val Gly Ser Pro Phe Leu Arg Leu 725 730 735 Pro Arg Leu Pro Leu Pro Leu Ala Arg Ala Ala Lys Pro Pro Pro Lys 740 745 750 Pro Arg Ser Ser Gln Pro Ser Thr Val Asp Leu Ala Ser Lys Val Lys 755 760 765 Leu Pro Glu Gly His Tyr Arg Val Gly Ser Arg Ala Ile Tyr Thr Cys 770 775 780 Glu Ser Arg Tyr Tyr Glu Leu Leu Gly Ser Gln Gly Arg Arg Cys Asp 785 790 795 800 Ser Asn Gly Asn Trp Ser Gly Arg Pro Ala Ser Cys Ile Pro Val Cys 805 810 815 Gly Arg Ser Asp Ser Pro Arg Ser Pro Phe Ile Trp Asn Gly Asn Ser 820 825 830 Thr Glu Ile Gly Gln Trp Pro Trp Gln Ala Gly Ile Ser Arg Trp Leu 835 840 845 Ala Asp His Asn Met Trp Phe Leu Gln Cys Gly Gly Ser Leu Leu Asn 850 855 860 Glu Lys Trp Ile Val Thr Ala Ala His Cys Val Thr Tyr Ser Ala Thr 865 870 875 880 Ala Glu Ile Ile Asp Pro Asn Gln Phe Lys Met Tyr Leu Gly Lys Tyr 885 890 895 Tyr Arg Asp Asp Ser Arg Asp Asp Asp Tyr Val Gln Val Arg Glu Ala 900 905 910 Leu Glu Ile His Val Asn Pro Asn Tyr Asp Pro Gly Asn Leu Asn Phe 915 920 925 Asp Ile Ala Leu Ile Gln Leu Lys Thr Pro Val Thr Leu Thr Thr Arg 930 935 940 Val Gln Pro Ile Cys Leu Pro Thr Asp Ile Thr Thr Arg Glu His Leu 945 950 955 960 Lys Glu Gly Thr Leu Ala Val Val Thr Gly Trp Gly Leu Asn Glu Asn 965 970 975 Asn Thr Tyr Ser Glu Thr Ile Gln Gln Ala Val Leu Pro Val Val Ala 980 985 990 Ala Ser Thr Cys Glu Glu Gly Tyr Lys Glu Ala Asp Leu Pro Leu Thr 995 1000 1005 Val Thr Glu Asn Met Phe Cys Ala Gly Tyr Lys Lys Gly Arg Tyr Asp 1010 1015 1020 Ala Cys Ser Gly Asp Ser Gly Gly Pro Leu Val Phe Ala Asp Asp Ser 1025 1030 1035 1040 Arg Thr Glu Arg Arg Trp Val Leu Glu Gly Ile Val Ser Trp Gly Ser 1045 1050 1055 Pro Ser Gly Cys Gly Lys Ala Asn Gln Tyr Gly Gly Phe Thr Lys Val 1060 1065 1070 Asn Val Phe Leu Ser Trp Ile Arg Gln Phe Ile 1075 1080 7 3438 DNA Carcinoscorpius rotundicauda 7 gtgaaggtaa cttaagtatg gtcttagcgt cgtttttggt gtctggttta gttctagggc 60 tactagccca aaaaatgcgc ccagttcagt ccaaaggagt agatctaggc ttgtgtgatg 120 aaacgaggtt cgagtgtaag tgtggcgatc caggctatgt gttcaacatt ccagtgaaac 180 aatgtacata cttttatcga tggaggccgt attgtaaacc atgtgatgac ctggaggcta 240 aggatatttg tccaaagtac aaacgatgtc aagagtgtaa ggctggtctt gatagttgtg 300 ttacttgtcc acctaacaaa tatggtactt ggtgtagcgg tgaatgtcag tgtaagaatg 360 gaggtatctg tgaccagagg acaggagctt gtgcatgtcg tgacagatat gaaggggtgc 420 actgtgaaat tctcaaaggt tgtcctcttc ttccatcgga ttctcaggtt caggaagtca 480 gaaatccacc agataatccc caaactattg actacagctg ttcaccaggg ttcaagctta 540 agggtatggc acgaattagc tgtctcccaa atggacagtg gagtaacttt ccacccaaat 600 gtattcgaga atgtgccatg gtttcatctc cagaacatgg gaaagtgaat gctcttagtg 660 gtgatatgat agaaggggct actttacggt tctcatgtga tagtccctac tacttgattg 720 gtcaagaaac attaacctgt cagggtaatg gtcagtggaa tggacagata ccacaatgta 780 agaacttggt cttctgtcct gacctggatc ctgtaaacca tgctgaacac aaggttaaaa 840 ttggtgtgga acaaaaatat ggtcagtttc ctcaaggcac tgaagtgacc tatacgtgtt 900 cgggtaacta cttcttgatg ggttttgaca ccttaaaatg taaccctgat gggtcttggt 960 caggatcaca gccatcctgt gttaaagtgg cagacagaga ggtcgactgt gacagtaaag 1020 ctgtagactt cttggatgat gttggtgaac ctgtcaggat ccactgtcct gctggctgtt 1080 ctttgacagc tggtactgtg tggggtacag ccatatacca tgaactttcc tcagtgtgtc 1140 gtgcagccat ccatgctggc aagcttccaa actctggagg agcggtgcat gttgtgaaca 1200 atggccccta ctcggacttt ctgggtagtg acctgaatgg gataaaatcg gaagagttga 1260 agtctcttgc ccggagtttc cgattcgatt atgtccgttc ctccacagca ggtaaatcag 1320 gatgtcctga tggatggttt gaggtagacg agaactgtgt gtacgttaca tcaaaacaga 1380 gagcctggga aagagctcaa ggtgtgtgta ccaatatggc tgctcgtctt gctgtgctgg 1440 acaaagatgt aattccaaat tcgttgactg agactctacg agggaaaggg ttaacaacca 1500 cgtggatagg attgcacaga ctagatgctg agaagccctt tatttgggag ttaatggatc 1560 gtagtaatgt ggttctgaat gataacctaa cattctgggc ctctggcgaa cctggaaatg 1620 aaactaactg tgtatatatg gacatccaag atcagttgca gtctgtgtgg aaaaccaagt 1680 catgttttca gccctcaagt tttgcttgca tgatggatct gtcagacaga aataaagcca 1740 aatgcgatga tcctggatca ctggaaaatg gacacgccac acttcatgga caaagtattg 1800 atgggttcta tgctggttct tctataaggt acagctgtga ggttctccac tacctcagtg 1860 gaactgaaac cgtaacttgt acaacaaatg gcacatggag tgctcctaaa cctcgatgta 1920 tcaaagtcat cacctgccaa aacccccctg taccatcata tggttctgtg gaaatcaaac 1980 ccccaagtcg gacaaactcg ataagtcgtg ttgggtcacc tttcttgagg ttgccacggt 2040 tacccctccc attagctaga gcagccaaac ctcctccaaa acctagatcc tcacaaccct 2100 ctactgtgga cttggcttct aaagttaaac tacctgaagg tcattaccgg gtagggtctc 2160 gagccatcta cacgtgcgag tcgagatact acgaactact tggatctcaa ggcagaagat 2220 gtgactctaa tggaaactgg agtggtcggc cagcgagctg tattccagtt tgtggacggt 2280 cagactctcc tcgttctcct tttatctgga atgggaattc tacagaaata ggtcagtggc 2340 cgtggcaggc aggaatctct agatggcttg cagaccacaa tatgtggttt ctccagtgtg 2400 gaggatctct attgaatgag aaatggatcg tcactgctgc ccactgtgtc acctactctg 2460 ctactgctga gattattgac cccaatcagt ttaaaatgta tctgggcaag tactaccgtg 2520 atgacagtag agacgatgac tatgtacaag taagagaggc tcttgagatc cacgtgaatc 2580 ctaactacga ccccggcaat ctcaactttg acatagccct aattcaactg aaaactcctg 2640 ttactttgac aacacgagtc caaccaatct gtctgcctac tgacatcaca acaagagaac 2700 acttgaagga gggaacatta gcagtggtga caggttgggg tttgaatgaa aacaacacct 2760 attcagagac gattcaacaa gctgtgctac ctgttgttgc agccagcacc tgtgaagagg 2820 ggtacaagga agcagactta ccactgacag taacagagaa catgttctgt gcaggttaca 2880 agaagggacg ttatgatgcc tgcagtgggg acagtggagg acctttagtg tttgctgatg 2940 attcccgtac cgaaaggcgg tgggtcttgg aagggattgt cagctggggc agtcccagtg 3000 gatgtggcaa ggcgaaccag tacgggggct tcactaaagt taacgttttc ctgtcatgga 3060 ttaggcagtt catttgaaac tgatctaaat attttaagca tggttataaa cgtcttgttt 3120 cctattattg ctttactagt ttaacccata agaaggttaa ctgggtaagg cacaaggatc 3180 attgtttctg tttgttttta caaatggtta ttttagtcag tgaatgagaa tagtatccat 3240 tgaagactgt taccttttat tctacctttt tatattacta tgtaagtatt tgggatatct 3300 tctacacatg aaaattctgt cattttacca taaatttggt ttctggtgtg tgctaagtcc 3360 accagtagag aacgatgtaa ttttcactag cacatgaaat aaatatagaa caaatctatt 3420 ataaactacc ttaaaaaa 3438 8 1019 PRT Carcinoscorpius rotundicauda 8 Met Val Leu Ala Ser Phe Leu Val Ser Gly Leu Val Leu Gly Leu Leu 1 5 10 15 Ala Gln Lys Met Arg Pro Val Gln Ser Lys Gly Val Asp Leu Gly Leu 20 25 30 Cys Asp Glu Thr Arg Phe Glu Cys Lys Cys Gly Asp Pro Gly Tyr Val 35 40 45 Phe Asn Ile Pro Val Lys Gln Cys Thr Tyr Phe Tyr Arg Trp Arg Pro 50 55 60 Tyr Cys Lys Pro Cys Asp Asp Leu Glu Ala Lys Asp Ile Cys Pro Lys 65 70 75 80 Tyr Lys Arg Cys Gln Glu Cys Lys Ala Gly Leu Asp Ser Cys Val Thr 85 90 95 Cys Pro Pro Asn Lys Tyr Gly Thr Trp Cys Ser Gly Glu Cys Gln Cys 100 105 110 Lys Asn Gly Gly Ile Cys Asp Gln Arg Thr Gly Ala Cys Ala Cys Arg 115 120 125 Asp Arg Tyr Glu Gly Val His Cys Glu Ile Leu Lys Gly Cys Pro Leu 130 135 140 Leu Pro Ser Asp Ser Gln Val Gln Glu Val Arg Asn Pro Pro Asp Asn 145 150 155 160 Pro Gln Thr Ile Asp Tyr Ser Cys Ser Pro Gly Phe Lys Leu Lys Gly 165 170 175 Met Ala Arg Ile Ser Cys Leu Pro Asn Gly Gln Trp Ser Asn Phe Pro 180 185 190 Pro Lys Cys Ile Arg Glu Cys Ala Met Val Ser Ser Pro Glu His Gly 195 200 205 Lys Val Asn Ala Leu Ser Gly Asp Met Ile Glu Gly Ala Thr Leu Arg 210 215 220 Phe Ser Cys Asp Ser Pro Tyr Tyr Leu Ile Gly Gln Glu Thr Leu Thr 225 230 235 240 Cys Gln Gly Asn Gly Gln Trp Asn Gly Gln Ile Pro Gln Cys Lys Asn 245 250 255 Leu Val Phe Cys Pro Asp Leu Asp Pro Val Asn His Ala Glu His Lys 260 265 270 Val Lys Ile Gly Val Glu Gln Lys Tyr Gly Gln Phe Pro Gln Gly Thr 275 280 285 Glu Val Thr Tyr Thr Cys Ser Gly Asn Tyr Phe Leu Met Gly Phe Asp 290 295 300 Thr Leu Lys Cys Asn Pro Asp Gly Ser Trp Ser Gly Ser Gln Pro Ser 305 310 315 320 Cys Val Lys Val Ala Asp Arg Glu Val Asp Cys Asp Ser Lys Ala Val 325 330 335 Asp Phe Leu Asp Asp Val Gly Glu Pro Val Arg Ile His Cys Pro Ala 340 345 350 Gly Cys Ser Leu Thr Ala Gly Thr Val Trp Gly Thr Ala Ile Tyr His 355 360 365 Glu Leu Ser Ser Val Cys Arg Ala Ala Ile His Ala Gly Lys Leu Pro 370 375 380 Asn Ser Gly Gly Ala Val His Val Val Asn Asn Gly Pro Tyr Ser Asp 385 390 395 400 Phe Leu Gly Ser Asp Leu Asn Gly Ile Lys Ser Glu Glu Leu Lys Ser 405 410 415 Leu Ala Arg Ser Phe Arg Phe Asp Tyr Val Arg Ser Ser Thr Ala Gly 420 425 430 Lys Ser Gly Cys Pro Asp Gly Trp Phe Glu Val Asp Glu Asn Cys Val 435 440 445 Tyr Val Thr Ser Lys Gln Arg Ala Trp Glu Arg Ala Gln Gly Val Cys 450 455 460 Thr Asn Met Ala Ala Arg Leu Ala Val Leu Asp Lys Asp Val Ile Pro 465 470 475 480 Asn Ser Leu Thr Glu Thr Leu Arg Gly Lys Gly Leu Thr Thr Thr Trp 485 490 495 Ile Gly Leu His Arg Leu Asp Ala Glu Lys Pro Phe Ile Trp Glu Leu 500 505 510 Met Asp Arg Ser Asn Val Val Leu Asn Asp Asn Leu Thr Phe Trp Ala 515 520 525 Ser Gly Glu Pro Gly Asn Glu Thr Asn Cys Val Tyr Met Asp Ile Gln 530 535 540 Asp Gln Leu Gln Ser Val Trp Lys Thr Lys Ser Cys Phe Gln Pro Ser 545 550 555 560 Ser Phe Ala Cys Met Met Asp Leu Ser Asp Arg Asn Lys Ala Lys Cys 565 570 575 Asp Asp Pro Gly Ser Leu Glu Asn Gly His Ala Thr Leu His Gly Gln 580 585 590 Ser Ile Asp Gly Phe Tyr Ala Gly Ser Ser Ile Arg Tyr Ser Cys Glu 595 600 605 Val Leu His Tyr Leu Ser Gly Thr Glu Thr Val Thr Cys Thr Thr Asn 610 615 620 Gly Thr Trp Ser Ala Pro Lys Pro Arg Cys Ile Lys Val Ile Thr Cys 625 630 635 640 Gln Asn Pro Pro Val Pro Ser Tyr Gly Ser Val Glu Ile Lys Pro Pro 645 650 655 Ser Arg Thr Asn Ser Ile Ser Arg Val Gly Ser Pro Phe Leu Arg Leu 660 665 670 Pro Arg Leu Pro Leu Pro Leu Ala Arg Ala Ala Lys Pro Pro Pro Lys 675 680 685 Pro Arg Ser Ser Gln Pro Ser Thr Val Asp Leu Ala Ser Lys Val Lys 690 695 700 Leu Pro Glu Gly His Tyr Arg Val Gly Ser Arg Ala Ile Tyr Thr Cys 705 710 715 720 Glu Ser Arg Tyr Tyr Glu Leu Leu Gly Ser Gln Gly Arg Arg Cys Asp 725 730 735 Ser Asn Gly Asn Trp Ser Gly Arg Pro Ala Ser Cys Ile Pro Val Cys 740 745 750 Gly Arg Ser Asp Ser Pro Arg Ser Pro Phe Ile Trp Asn Gly Asn Ser 755 760 765 Thr Glu Ile Gly Gln Trp Pro Trp Gln Ala Gly Ile Ser Arg Trp Leu 770 775 780 Ala Asp His Asn Met Trp Phe Leu Gln Cys Gly Gly Ser Leu Leu Asn 785 790 795 800 Glu Lys Trp Ile Val Thr Ala Ala His Cys Val Thr Tyr Ser Ala Thr 805 810 815 Ala Glu Ile Ile Asp Pro Asn Gln Phe Lys Met Tyr Leu Gly Lys Tyr 820 825 830 Tyr Arg Asp Asp Ser Arg Asp Asp Asp Tyr Val Gln Val Arg Glu Ala 835 840 845 Leu Glu Ile His Val Asn Pro Asn Tyr Asp Pro Gly Asn Leu Asn Phe 850 855 860 Asp Ile Ala Leu Ile Gln Leu Lys Thr Pro Val Thr Leu Thr Thr Arg 865 870 875 880 Val Gln Pro Ile Cys Leu Pro Thr Asp Ile Thr Thr Arg Glu His Leu 885 890 895 Lys Glu Gly Thr Leu Ala Val Val Thr Gly Trp Gly Leu Asn Glu Asn 900 905 910 Asn Thr Tyr Ser Glu Thr Ile Gln Gln Ala Val Leu Pro Val Val Ala 915 920 925 Ala Ser Thr Cys Glu Glu Gly Tyr Lys Glu Ala Asp Leu Pro Leu Thr 930 935 940 Val Thr Glu Asn Met Phe Cys Ala Gly Tyr Lys Lys Gly Arg Tyr Asp 945 950 955 960 Ala Cys Ser Gly Asp Ser Gly Gly Pro Leu Val Phe Ala Asp Asp Ser 965 970 975 Arg Thr Glu Arg Arg Trp Val Leu Glu Gly Ile Val Ser Trp Gly Ser 980 985 990 Pro Ser Gly Cys Gly Lys Ala Asn Gln Tyr Gly Gly Phe Thr Lys Val 995 1000 1005 Asn Val Phe Leu Ser Trp Ile Arg Gln Phe Ile 1010 1015 

1. A reagent for detecting endotoxin, comprising: a purified horseshoe crab Factor C protein; and a surfactant.
 2. The reagent of claim 1 wherein the surfactant is selected from the group consisting of: (I) amphoteric surfactants represented by the following formulae

 wherein R₁ is an alkylene radical having from 1 to 4 carbon atoms;  Y and Y′ are each (1) hydrogen, (2) lower alkyl, or (3) hydroxy lower alkyl;  R₂ and R₃ are each (1) lower alkyl or (2) hydroxy lower alkyl;  n is 0 or 1, when n is 0, R₄ is alkyl containing from about 8 to about 18 carbon atoms;  when n is 1, R₄ is an alkylene radical having from 1 to about 6 carbon atoms;  R₅ is an alkyl containing from about 8 to about 18 carbon atoms; and  M is hydrogen, sodium, potassium or ammonium; (II) anionic surfactants represented by the following formulae: (R₆)_(n1-)(Y)Ar(SO₃M)_(n2)  (E) R₅OSO₃M  (F)  wherein  R₅, Y, and M have the same meaning as set forth above;  R₆ is an alkyl from 8 to 24 carbon atoms;  n1 is an integer from 1 to 3;  n2 is 1 or 2; and  Ar is phenyl or naphthyl; (III) cationic surfactants represented by the following formula:

 wherein R₅, Y, and Y′ have the same meaning as set forth above; (IV) nonionic surfactants represented by the following formula: R₅R₇R₈N→O  (H)  wherein  R₅ has the same meaning as set forth above;  R₇ and R₈ are each methyl or ethyl; and (V) those nonionic surfactants selected from the group consisting of the condensation product of about 10 to 30 moles of ethylene oxide with the monoester of a hexahydric alcohol containing 6 carbon atoms with the ester group containing 10 to 20 carbon atoms.
 3. The reagent of claim 1 wherein the horseshoe crab is Limulus polyphemus.
 4. The reagent of claim 1 wherein the horseshoe crab is Carcinoscorpius rotundicauda.
 5. The reagent of claim 1 wherein the horseshoe crab is Tachypleus tridentatus.
 6. The reagent of claim 1 wherein the horseshoe crab is Tachypleus gigas.
 7. The reagent of claim 1 wherein the Factor C protein is made by the method of culturing a host cell comprising a vector encoding the Factor C protein in a supernatant under conditions such that the Factor C protein is expressed into the superatant.
 8. The reagent of claim 7 wherein the host cell is an Sf9 cell.
 9. The reagent of claim 7 wherein the horseshoe crab is Carcinoscorpius rotundicauda.
 10. (canceled)
 11. A method of detecting endotoxin in a test sample, comprising the steps of: contacting a test sample with (1) a reagent comprising (a) a purified horseshoe crab Factor C protein and (b) a surfactant and (2) a Factor C substrate, wherein cleavage of the Factor C substrate generates a detectable signal to form a contacted test sample to form a test sample-reagent-substrate mixture; and assaying the contacted test sample for the presence or absence of the detectable signal, wherein an amount of the detectable signal that is increased relative to a control sample that does not contain endotoxin indicates a presence of endotoxin in the test sample.
 12. The method of claim 11 wherein the horseshoe crab is Limulus polyphemus.
 13. The method of claim 11 wherein the horseshoe crab is Carcinoscorpius rotundicauda.
 14. The method of claim 11 wherein the horseshoe crab is Tachypleus tridentatus.
 15. The method of claim 11 wherein the horseshoe crab is Tachypleus gigas.
 16. The method of claim 11 wherein the Factor C protein is made by the method of: culturing a host cell comprising a vector encoding the Factor C protein in a supernatant under conditions such that the Factor C protein is expressed into the supernatant
 17. The method of claim 16 wherein the host cell is an Sf9 cell.
 18. The method of claim 15 wherein the horseshoe crab is Carcinoscorpius rotundicauda.
 19. (canceled)
 20. The method of claim 11 wherein the Factor C substrate is selected from the group consisting of N-t-BOC-Asp(Obzl)-Pro-Arg-7-Amido-4-methyl coumarin and N-t-BOC-Val-Pro-Arg-7-Amido-4-methyl coumarin.
 21. A method of detecting endotoxin in a test sample, comprising the steps of: contacting a test sample with (1) a reagent comprising (a) a recombinant Carcinoscorpius rotundicauda Factor C protein, wherein the Factor C protein is made by the method of culturing a host cell comprising a vector encoding the Factor C protein in a supernatant under conditions such that the Factor C protein is expressed into the supernatant and (b) a surfactant and (2) N-t-BOC-Asp(Obzl)-Pro-Arg-7-Amido-4-methyl coumarin to form a contacted test sample; and assaying the contacted test sample for the presence or absence of a fluorescent signal, wherein an amount of the fluorescent signal that is increased relative to a control sample that does not contain endotoxin indicates a presence of endotoxin in the test sample.
 22. The method of claim 21 wherein the host cell is an Sf9 cell.
 23. A kit for detecting endotoxin, comprising: a reagent that comprises (a) a purified horseshoe crab Factor C protein and (b) a surfactant; and instructions for performing the method of claim
 11. 24. The kit of claim 23 further comprising a Factor C substrate, wherein cleavage of the Factor C substrate generates a detectable signal.
 25. The kit of claim 24 wherein the Factor C substrate is selected from the group consisting of N-t-BOC-Asp(Obzl)-Pro-Arg-7-Amido-4-methyl coumarin and N-t-BOC-Val-Pro-Arg-7-Amido-4-methyl coumarin.
 26. The kit of claim 23 wherein the purified Factor C is made by the method of culturing a host cell comprising a vector encoding the Factor C protein in a supernatant under conditions such that the Factor C protein is expressed into the supernatant.
 27. The kit of claim 26 wherein the host cell is an Sf9 cell.
 28. A method of detecting endotoxin in a test sample, comprising the steps of: contacting a test sample with a reagent comprising (a) a purified horseshoe crab Factor C protein and (b) a surfactant to form a test sample-reagent mixture; contacting the test sample-reagent mixture with a Factor C substrate, wherein cleavage of the Factor C substrate generates a detectable signal; and assaying the contacted test sample-reagent mixture for the presence or absence of the detectable signal, wherein an amount of the detectable signal that is increased relative to a control sample that does not contain endotoxin indicates a presence of endotoxin in the test sample.
 29. A method of detecting endotoxin in a test sample, comprising the steps of: contacting a test sample with a reagent comprising (a) a recombinant Carcinoscorpius rotundicauda Factor C protein, wherein the Factor C protein is made by the method of culturing a host cell comprising a vector encoding the Factor C protein in a supernatant under conditions such that the Factor C protein is expressed into the supernatant and (b) a surfactant to form a test sample-reagent mixture; contacting the test sample-reagent mixture with N-t-BOC-Asp(Obzl)-Pro-Arg-7-Amido-4-methyl coumarin; and assaying the contacted test sample-reagent mixture for the presence or absence of a fluorescent signal, wherein an amount of the fluorescent signal that is increased relative to a control sample that does not contain endotoxin indicates a presence of endotoxin in the test sample.
 30. The reagent of claim 1 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 31. The reagent of claim 2 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 32. The reagent of claim 3 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 33. The reagent of claim 4 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 34. The reagent of claim 5 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 35. The reagent of claim 6 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 36. The reagent of claim 7 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 37. The reagent of claim 8 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 38. The reagent of claim 9 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 39. The method of claim 11 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 40. The method of claim 12 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 41. The method of claim 13 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 42. The method of claim 14 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 43. The method of claim 15 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 44. The method of claim 16 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 45. The method of claim 17 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 46. The method of claim 18 wherein the surfactant is selected from the group consisting of ZWITTERGENT 3-14, Triton X-100, Triton X-114, octyl-beta-D-thioglucoside, Genapol C-100, Tween 20, and Tween
 80. 